1
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Flowers AM, Brown A, Klobukowski M. Anharmonic Vibrational Spectroscopy of Germanium-Containing Clusters, Ge xC 4-x and Ge xSi 4-x ( x = 0-4), for Interstellar Detection. J Phys Chem A 2024; 128:5351-5361. [PMID: 38942734 DOI: 10.1021/acs.jpca.4c02081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/30/2024]
Abstract
An extensive, high-level theoretical study on tetra-atomic germanium carbide/silicide clusters is presented. Accurate harmonic and anharmonic vibrational frequencies and rotational constants are calculated at the CCSD(T)-F12a(b)/cc-pVT(Q)Z-F12 levels of theory. With growing capabilities to discern more of the chemical composition of the interstellar medium (ISM), an accurate database of reference material is required. The presence of carbon is ubiquitous in the ISM, and silicon is known to be present in interstellar dust grains; however, germanium-containing molecules remain elusive. To begin understanding the presence and role of germanium in the ISM, we present this study of the vibrational and rotational spectroscopic properties of various germanium-containing molecules to aid in their potential identification in the ISM with modern observational tools such as the James Webb Space Telescope. Structures studied herein include rhomboidal (r-), diamond (d-), and trapezoidal (t-) tetra-atomic molecules of the form GexC4-x and GexSi4-x, where x = 0-4. The most promising structure for detection is r-Ge2C2 via the ν4 mode with a frequency of 802.7 cm-1 (12.5 μm) and an intensity of 307.2 km mol-1. Other molecules that are potentially detectable, i.e., through vibrational modes or rotational transitions, include r-Ge3C, r-GeSi3, d-GeC3, r-GeC3, and t-Ge2C2.
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Affiliation(s)
- A Mackenzie Flowers
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Alex Brown
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Mariusz Klobukowski
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
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2
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de Moraes MMF, Tecmer P. Towards reliable and efficient modeling of [Cu 2O 2] 2+-based compound electronic structures with the partially fixed reference space protocols. Phys Chem Chem Phys 2024. [PMID: 38984390 DOI: 10.1039/d4cp01309c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/11/2024]
Abstract
This work reports a computationally efficient approach for reliable modeling of complex electronic structures based on [Cu2O2]2+ moieties. Specifically, we explore the recently developed partially fixed reference space (PFRS) protocol to minimize the active space size, taking into account the double d-shell effects. We show that the ground-state electronic structure of the core [Cu2O2]2+ model system is dominated by the d9/d10 occupations. The PFRS-crafted active spaces are further used to generate the reference wave functions for the multi-reference coupled cluster, configuration interaction, and multi-reference perturbation theory calculations. Specifically, we demonstrate that the bare [Cu2O2]2+ core can be modeled qualitatively using active spaces as small as CAS(2,2)PFRS. To obtain quantitative agreement with the reference DMRG(32,62)CI calculations, the CAS(4,4) has to be used in conjunction with the MRCCSD correction on top of it. This reliable and computationally efficient protocol is further used to model the electronic structure and properties of ammonia coordinated [Cu2O2]2+ complexes. Finally, based on the large amount of available experimental data regarding the oxo-peroxo equilibrium of [Cu2O2]2+-based systems, it is possible to formulate educated guesses regarding the effect of each experimental variable over each d-occupancy-specific state. With a large sample size of d-occupancy-specific state dependence with ligands and solvents, it should be possible to propose new ligands with specific d-occupancy and, therefore, oxidative properties based on the d-occupancy energy gaps of relatively low-cost calculations.
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Affiliation(s)
- Matheus Morato F de Moraes
- Institute of Physics, Faculty of Physics, Astronomy, and Informatics, Nicolaus Copernicus University in Toruń, Grudziadzka 5, 87-100 Toruń, Poland.
| | - Paweł Tecmer
- Institute of Physics, Faculty of Physics, Astronomy, and Informatics, Nicolaus Copernicus University in Toruń, Grudziadzka 5, 87-100 Toruń, Poland.
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3
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Ariyarathna IR. Ab initio exploration of low-lying electronic states of linear and bent MNX + (M = Ca, Sr, Ba, Ra; X = O, S, Se, Te, Po) and their origins. J Comput Chem 2024. [PMID: 38981130 DOI: 10.1002/jcc.27456] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2024] [Revised: 06/10/2024] [Accepted: 06/12/2024] [Indexed: 07/11/2024]
Abstract
High-level multireference and coupled cluster quantum calculations were employed to analyze low-lying electronic states of linear-MNX+ and side-bonded-M[NX]+ (M = Ca, Sr, Ba, Ra; X = O, S, Se, Te, Po) species. Their full potential energy curves (PECs), dissociation energies (Des), geometric parameters, excitation energies (Tes), and harmonic vibrational frequencies (ωes) are reported. The first three chemically bound electronic states of MNX+ and M[NX]+ are 3Σ-, 1Δ, 1Σ+ and 3A″, 1A', 1A″, respectively. The 3Σ-, 1Δ, 1Σ+ of MNX+ originate from the M+(2D) + NX(2Π) fragments, whereas the 3A″, 1A', 1A″ states of M[NX]+ dissociate to M+(2S) + NX(2Π) as a result of avoided crossings. The MNX+ and M[NX]+ are real minima on the potential energy surface and their interconversions are possible. The M2+NX-/M2+[NX]- ionic structure is an accurate representation for their low-lying electronic states. The Des of MNX+ species were found to depend on the dipole moment (μ) of the corresponding NX ligands and a linear relationship between these two parameters was observed.
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Affiliation(s)
- Isuru R Ariyarathna
- Physics and Chemistry of Materials (T-1), Los Alamos National Laboratory, Los Alamos, New Mexico, USA
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4
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Greiner J, Gianni I, Nottoli T, Lipparini F, Eriksen JJ, Gauss J. MBE-CASSCF Approach for the Accurate Treatment of Large Active Spaces. J Chem Theory Comput 2024; 20:4663-4675. [PMID: 38809011 DOI: 10.1021/acs.jctc.4c00388] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2024]
Abstract
We present a novel implementation of the complete active space self-consistent field (CASSCF) method that makes use of the many-body expanded full configuration interaction (MBE-FCI) method to incrementally approximate electronic structures within large active spaces. On the basis of a hybrid first-order algorithm employing both Super-CI and quasi-Newton strategies for the optimization of molecular orbitals, we demonstrate both computational efficacy and high accuracy of the resulting MBE-CASSCF method. We assess the performance of our implementation on a set of established numerical tests before applying MBE-CASSCF in the investigation of the triplet-quintet spin gap of iron(II) porphyrin with active spaces as large as 50 electrons in 50 orbitals.
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Affiliation(s)
- Jonas Greiner
- Department Chemie, Johannes Gutenberg-Universität Mainz, Duesbergweg 10-14, Mainz 55128, Germany
| | - Ivan Gianni
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via G. Moruzzi 13, Pisa 56124, Italy
| | - Tommaso Nottoli
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via G. Moruzzi 13, Pisa 56124, Italy
| | - Filippo Lipparini
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via G. Moruzzi 13, Pisa 56124, Italy
| | - Janus J Eriksen
- DTU Chemistry, Technical University of Denmark, Kemitorvet Bldg. 206, Kgs. Lyngby 2800, Denmark
| | - Jürgen Gauss
- Department Chemie, Johannes Gutenberg-Universität Mainz, Duesbergweg 10-14, Mainz 55128, Germany
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5
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Trabelsi T, Francisco JS. Exploring the photochemistry of OAlOH: Photodissociation pathways and electronic spectra. J Chem Phys 2024; 160:204304. [PMID: 38804488 DOI: 10.1063/5.0207398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2024] [Accepted: 05/08/2024] [Indexed: 05/29/2024] Open
Abstract
This study was focused on the photochemistry of OAlOH and three possible pathways, which were studied with high-level multireference configuration interaction ab initio calculations. We computed cuts of the six-dimensional potential energy surfaces for the ground, the lowest singlet and triplet excited states, and probed the photodissociation mechanisms and the stabilities. The OAlOH electronic spectrum, with an energy reaching 7.15 eV, contained four prominent peaks. Photodissociation to AlO, OH, and AlOH constituted a plausible mechanism within the deep-UV range (λ = 250.4 nm). Our data indicated the photostability of OAlOH in the near-UV‒Vis region, so detection with laser-induced fluorescence is possible. Fluorescence and phosphorescence may occur upon excitation at 363.5 nm. The roles of OAlOH in the photochemical reactions of Al-bearing molecules in the upper atmosphere and VY Canis Majoris are discussed.
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Affiliation(s)
- Tarek Trabelsi
- Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6243, USA
| | - Joseph S Francisco
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
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6
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Fitzpatrick A, Nykänen A, Talarico NW, Lunghi A, Maniscalco S, García-Pérez G, Knecht S. Self-Consistent Field Approach for the Variational Quantum Eigensolver: Orbital Optimization Goes Adaptive. J Phys Chem A 2024; 128:2843-2856. [PMID: 38547028 DOI: 10.1021/acs.jpca.3c05882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/12/2024]
Abstract
We present a self-consistent field (SCF) approach within the adaptive derivative-assembled problem-tailored ansatz variational quantum eigensolver (ADAPT-VQE) framework for efficient quantum simulations of chemical systems on near-term quantum computers. To this end, our ADAPT-VQE-SCF approach combines the idea of generating an ansatz with a small number of parameters, resulting in shallow-depth quantum circuits with a direct minimization of an energy expression that is correct to second order with respect to changes in the molecular orbital basis. Our numerical analysis, including calculations for the transition-metal complex ferrocene [Fe (C5H5)2], indicates that convergence in the self-consistent orbital optimization loop can be reached without a considerable increase in the number of two-qubit gates in the quantum circuit by comparison to a VQE optimization in the initial molecular orbital basis. Moreover, the orbital optimization can be carried out simultaneously within each iteration of the ADAPT-VQE cycle. ADAPT-VQE-SCF thus allows us to implement a routine analogous to the complete active space SCF, a cornerstone of state-of-the-art computational chemistry, in a hardware-efficient manner on near-term quantum computers. Hence, ADAPT-VQE-SCF paves the way toward a paradigm shift for quantitative quantum-chemistry simulations on quantum computers by requiring fewer qubits and opening up for the use of large and flexible atomic orbital basis sets in contrast to earlier methods that are predominantly based on the idea of full active spaces with minimal basis sets.
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Affiliation(s)
- Aaron Fitzpatrick
- Algorithmiq Ltd, Kanavakatu 3C, Helsinki FI-00160, Finland
- Trinity Quantum Alliance, Unit 16, Trinity Technology and Enterprise Centre, Pearse Street, Dublin 2 D02 YN67, Ireland
| | - Anton Nykänen
- Algorithmiq Ltd, Kanavakatu 3C, Helsinki FI-00160, Finland
| | | | - Alessandro Lunghi
- School of Physics, AMBER and CRANN Institute, Trinity College, Dublin 2, Ireland
| | | | | | - Stefan Knecht
- Algorithmiq Ltd, Kanavakatu 3C, Helsinki FI-00160, Finland
- ETH Zürich, Department of Chemistry and Applied Life Sciences Vladimir-Prelog-Weg 1-5/10, Zürich 8093, Switzerland
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7
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Beck IT, Lahm ME, Douberly GE, Schaefer HF. Convergent ab initio analysis of the multi-channel HOBr + H reaction. J Chem Phys 2024; 160:124304. [PMID: 38516979 DOI: 10.1063/5.0200276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Accepted: 03/06/2024] [Indexed: 03/23/2024] Open
Abstract
High-level potential energy surfaces for three reactions of hypobromous acid with atomic hydrogen were computed at the CCSDTQ/CBS//CCSDT(Q)/complete basis set level of theory. Focal point analysis was utilized to extrapolate energies and gradients for energetics and optimizations, respectively. The H attack at Br and subsequent Br-O cleavage were found to proceed barrierlessly. The slightly submerged transition state lies -0.2 kcal mol-1 lower in energy than the reactants and produces OH and HBr. The two other studied reaction paths are the radical substitution to produce H2O and Br with a 4.0 kcal mol-1 barrier and the abstraction at hydrogen to produce BrO and H2 with an 11.2 kcal mol-1 barrier. The final product energies lie -37.2, -67.9, and -7.3 kcal mol-1 lower in energy than reactants, HOBr + H, for the sets of products OH + HBr, H2O + Br, and H2 + BrO, respectively. Additive corrections computed for the final energetics, particularly the zero-point vibrational energies and spin-orbit corrections, significantly impacted the final stationary point energies, with corrections up to 6.2 kcal mol-1.
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Affiliation(s)
- Ian T Beck
- Department of Chemistry and Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602, USA
| | - Mitchell E Lahm
- Department of Chemistry and Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602, USA
| | - Gary E Douberly
- Department of Chemistry and Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602, USA
| | - Henry F Schaefer
- Department of Chemistry and Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602, USA
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8
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Lam TL, Li H, Tan K, Chen Z, Tang YK, Yang J, Cheng G, Dai L, Che CM. Sterically Hindered Tetradentate [Pt(O^N^C^N)] Emitters with Radiative Decay Rates up to 5.3 × 10 5 s -1 for Phosphorescent Organic Light-Emitting Diodes with LT 95 Lifetime over 9200 h at 1000 cd m -2. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2307393. [PMID: 37897146 DOI: 10.1002/smll.202307393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Revised: 10/07/2023] [Indexed: 10/29/2023]
Abstract
Described here are sterically hindered tetradentate [Pt(O^N^C^N)] emitters (Pt-1, Pt-2, and Pt-3) developed for stable and high-performance green phosphorescent organic light-emitting diodes (OLEDs). These Pt(II) emitters exhibit strong saturated green phosphorescence (λmax = 517-531 nm) in toluene and mCP thin films with emission quantum yields as high as 0.97, radiative rate constants (kr) as high as 4.4-5.3 × 105 s-1 and reduced excimer emission, and with a preferential horizontally oriented transition dipole ratio of up to 84%. Theoretical calculations show that p-(hetero)arene substituents at the periphery of the ligand scaffolds in Pt-1, Pt-2, and Pt-3 can i) enhance the spin-orbit coupling (SOC) between the lower singlet excited states and the T1 state, and S0→Sn (n = 1 or 2) transition dipole moment, and ii) introducing additional SOC activity and the bright 1ILCT[π(carbazole)→π*(N^C^N)] excited state (Pt-2 and Pt-3), which are the main contributors to the increased kr values. Utilizing these tetradentate Pt(II) emitters, green phosphorescent OLEDs are fabricated with narrow-band electroluminescence (FWHM down to 36 nm), high external quantum efficiency, current efficiency up to 27.6% and 98.7 cd A-1, and an unprecedented device lifetime (LT95) of up to 9270 h at 1000 cd m-2 under laboratory conditions.
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Affiliation(s)
- Tsz-Lung Lam
- State Key Laboratory of Synthetic Chemistry, HKU-CAS Joint Laboratory on New Materials, Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China
- Hong Kong Quantum AI Lab Limited, Units 909-915, Building 17 W, 17 Science Park West Avenue, Hong Kong Science Park, Pak Shek Kok, Hong Kong
| | - Huiyang Li
- State Key Laboratory of Synthetic Chemistry, HKU-CAS Joint Laboratory on New Materials, Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China
- Guangdong Aglaia Optoelectronic Materials Co., Ltd, Foshan, 528300, China
| | - Kaixin Tan
- State Key Laboratory of Synthetic Chemistry, HKU-CAS Joint Laboratory on New Materials, Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China
| | - Ziyong Chen
- State Key Laboratory of Synthetic Chemistry, HKU-CAS Joint Laboratory on New Materials, Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China
| | - Yu-Kan Tang
- State Key Laboratory of Synthetic Chemistry, HKU-CAS Joint Laboratory on New Materials, Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China
| | - Jun Yang
- State Key Laboratory of Synthetic Chemistry, HKU-CAS Joint Laboratory on New Materials, Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China
- Hong Kong Quantum AI Lab Limited, Units 909-915, Building 17 W, 17 Science Park West Avenue, Hong Kong Science Park, Pak Shek Kok, Hong Kong
| | - Gang Cheng
- State Key Laboratory of Synthetic Chemistry, HKU-CAS Joint Laboratory on New Materials, Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China
- Hong Kong Quantum AI Lab Limited, Units 909-915, Building 17 W, 17 Science Park West Avenue, Hong Kong Science Park, Pak Shek Kok, Hong Kong
- HKU Shenzhen Institute of Research and Innovation, Shenzhen, Guangdong, 518057, P. R. China
| | - Lei Dai
- Guangdong Aglaia Optoelectronic Materials Co., Ltd, Foshan, 528300, China
| | - Chi-Ming Che
- State Key Laboratory of Synthetic Chemistry, HKU-CAS Joint Laboratory on New Materials, Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China
- Hong Kong Quantum AI Lab Limited, Units 909-915, Building 17 W, 17 Science Park West Avenue, Hong Kong Science Park, Pak Shek Kok, Hong Kong
- HKU Shenzhen Institute of Research and Innovation, Shenzhen, Guangdong, 518057, P. R. China
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9
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Slattery SA, Surjuse KA, Peterson CC, Penchoff DA, Valeev EF. Economical quasi-Newton unitary optimization of electronic orbitals. Phys Chem Chem Phys 2024; 26:6557-6573. [PMID: 38329140 DOI: 10.1039/d3cp05557d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
We present an efficient quasi-Newton orbital solver optimized to reduce the number of gradient evaluations and other computational steps of comparable cost. The solver optimizes orthogonal orbitals by sequences of unitary rotations generated by the (preconditioned) limited-memory Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) algorithm equipped with trust-region step restriction. The low-rank structure of the L-BFGS inverse Hessian is exploited when solving the trust-region problem. The efficiency of the proposed "Quasi-Newton Unitary Optimization with Trust-Region" (QUOTR) solver is compared to that of the standard Roothaan-Hall approach accelerated by the Direct Inversion of Iterative Subspace (DIIS), and other exact and approximate Newton solvers for mean-field (Hartree-Fock and Kohn-Sham) problems.
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Affiliation(s)
| | | | - Charles C Peterson
- Office of Advanced Research Computing, University of California, Los Angeles, CA 90095, USA
| | - Deborah A Penchoff
- UT Innovative Computing Laboratory, University of Tennessee, Knoxville, TN 37996, USA
| | - Edward F Valeev
- Department of Chemistry, Virginia Tech, Blacksburg, VA 24061, USA.
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10
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Chen J, Lane JR, Bates KH, Kjaergaard HG. Atmospheric Gas-Phase Formation of Methanesulfonic Acid. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:21168-21177. [PMID: 38051922 DOI: 10.1021/acs.est.3c07120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/07/2023]
Abstract
Despite its impact on the climate, the mechanism of methanesulfonic acid (MSA) formation in the oxidation of dimethyl sulfide (DMS) remains unclear. The DMS + OH reaction is known to form methanesulfinic acid (MSIA), methane sulfenic acid (MSEA), the methylthio radical (CH3S), and hydroperoxymethyl thioformate (HPMTF). Among them, HPMTF reacts further to form SO2 and OCS, while the other three form the CH3SO2 radical. Based on theoretical calculations, we find that the CH3SO2 radical can add O2 to form CH3S(O)2OO, which can react further to form MSA. The branching ratio is highly temperature sensitive, and the MSA yield increases with decreasing temperature. In warmer regions, SO2 is the dominant product of DMS oxidation, while in colder regions, large amounts of MSA can form. Global modeling indicates that the proposed temperature-sensitive MSA formation mechanism leads to a substantial increase in the simulated global atmospheric MSA formation and burden.
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Affiliation(s)
- Jing Chen
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, Copenhagen Ø DK-2100, Denmark
| | - Joseph R Lane
- School of Science, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand
| | - Kelvin H Bates
- NOAA Chemical Sciences Laboratory, Earth System Research Laboratories & Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado 80305, United States
| | - Henrik G Kjaergaard
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, Copenhagen Ø DK-2100, Denmark
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11
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Ding L, Knecht S, Schilling C. Quantum Information-Assisted Complete Active Space Optimization (QICAS). J Phys Chem Lett 2023:11022-11029. [PMID: 38047727 DOI: 10.1021/acs.jpclett.3c02536] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2023]
Abstract
We propose an effective quantum information-assisted complete active space optimization scheme (QICAS). What sets QICAS apart from other correlation-based selection schemes is (i) the use of unique measures from quantum information that assess the correlation in electronic structures in an unambiguous and predictive manner and (ii) an orbital optimization step that minimizes the correlation discarded by the active space approximation. Equipped with these features, QICAS yields, for smaller correlated molecule, sets of optimized orbitals with respect to which the complete active space configuration interaction energy reaches the corresponding complete active space self-consistent field (CASSCF) energy within chemical accuracy. For more challenging systems such as the chromium dimer, QICAS offers an excellent starting point for CASSCF by greatly reducing the number of iterations required for numerical convergence. Accordingly, our study validates a profound empirical conjecture: the energetically optimal nonactive spaces are predominantly those that contain the least entanglement.
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Affiliation(s)
- Lexin Ding
- Faculty of Physics, Arnold Sommerfeld Centre for Theoretical Physics (ASC), Ludwig-Maximilians-Universität München, Theresienstr. 37, 80333 München, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstrasse 4, 80799 München, Germany
| | - Stefan Knecht
- Algorithmiq Ltd., Kanavakatu 3C, FI-00160 Helsinki, Finland
- ETH Zürich, Laboratory for Physical Chemistry, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - Christian Schilling
- Faculty of Physics, Arnold Sommerfeld Centre for Theoretical Physics (ASC), Ludwig-Maximilians-Universität München, Theresienstr. 37, 80333 München, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstrasse 4, 80799 München, Germany
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12
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Craciunescu L, Liane EM, Kirrander A, Paterson MJ. Excited-state van der Waals potential energy surfaces for the NO A2Σ+ + CO2X1Σg+ collision complex. J Chem Phys 2023; 159:124303. [PMID: 38127380 DOI: 10.1063/5.0165769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Accepted: 09/06/2023] [Indexed: 12/23/2023] Open
Abstract
Excited state van der Waals (vdW) potential energy surfaces (PESs) of the NO A2Σ+ + CO2X1Σg+ system are thoroughly investigated using coupled cluster theory and complete active space perturbation theory to second order (CASPT2). First, it is shown that pair natural orbital coupled cluster singles and doubles with perturbative triples yields comparable accuracy compared to CCSD(T) for molecular properties and vdW-minima at a fraction of computational cost of the latter. Using this method in conjunction with highly diffuse basis sets and counterpoise correction for basis set superposition error, the PESs for different intermolecular orientations are investigated. These show numerous vdW-wells, interconnected for all geometries except one, with a maximum depth of up to 830 cm-1; considerably deeper than those on the ground state surface. Multi-reference effects are investigated with CASPT2 calculations. The long-range vdW-surfaces support recent experimental observations relating to rotational energy transfer due the anisotropy in the potentials.
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Affiliation(s)
- Luca Craciunescu
- Institute of Chemical Sciences, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, Scotland EH14 4AS, United Kingdom
| | - Eirik M Liane
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, OX1 3QZ Oxford, United Kingdom
| | - Adam Kirrander
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, OX1 3QZ Oxford, United Kingdom
| | - Martin J Paterson
- Institute of Chemical Sciences, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, Scotland EH14 4AS, United Kingdom
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13
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Szczepkowski J, Gronowski M, Grochola A, Jastrzebski W, Tomza M, Kowalczyk P. Excited Electronic States of Sr 2: Ab Initio Predictions and Experimental Observation of the 2 1Σ u+ State. J Phys Chem A 2023; 127:4473-4482. [PMID: 37192534 DOI: 10.1021/acs.jpca.3c02056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Despite its apparently simple nature with four valence electrons, the strontium dimer constitutes a challenge for modern electronic structure theory. Here we focus on excited electronic states of Sr2, which we investigate theoretically up to 25000 cm-1 above the ground state, to guide and explain new spectroscopic measurements. In particular, we focus on potential energy curves for the 11Σu+, 21Σu+, 11Πu, 21Πu, and 11Δu states computed using several variants of ab initio coupled-cluster and configuration-interaction methods to benchmark them. In addition, a new experimental study of the excited 21Σu+ state using polarization labeling spectroscopy is presented, which extends knowledge of this state to high vibrational levels, where perturbation by higher electronic states is observed. The available experimental observations are compared with the theoretical predictions and help to assess the accuracy and limitations of employed theoretical models. The present results pave the way for future more accurate theoretical and experimental spectroscopic studies.
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Affiliation(s)
- Jacek Szczepkowski
- Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warsaw, Poland
| | - Marcin Gronowski
- Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warszawa, Poland
| | - Anna Grochola
- Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warsaw, Poland
| | | | - Michał Tomza
- Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warszawa, Poland
| | - Paweł Kowalczyk
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warszawa, Poland
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14
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Marie A, Burton HGA. Excited States, Symmetry Breaking, and Unphysical Solutions in State-Specific CASSCF Theory. J Phys Chem A 2023; 127:4538-4552. [PMID: 37141564 DOI: 10.1021/acs.jpca.3c00603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
State-specific electronic structure theory provides a route toward balanced excited-state wave functions by exploiting higher-energy stationary points of the electronic energy. Multiconfigurational wave function approximations can describe both closed- and open-shell excited states and avoid the issues associated with state-averaged approaches. We investigate the existence of higher-energy solutions in complete active space self-consistent field (CASSCF) theory and characterize their topological properties. We demonstrate that state-specific approximations can provide accurate higher-energy excited states in H2 (6-31G) with more compact active spaces than would be required in a state-averaged formalism. We then elucidate the unphysical stationary points, demonstrating that they arise from redundant orbitals when the active space is too large or symmetry breaking when the active space is too small. Furthermore, we investigate the singlet-triplet crossing in CH2 (6-31G) and the avoided crossing in LiF (6-31G), revealing the severity of root flipping and demonstrating that state-specific solutions can behave quasi-diabatically or adiabatically. These results elucidate the complexity of the CASSCF energy landscape, highlighting the advantages and challenges of practical state-specific calculations.
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Affiliation(s)
- Antoine Marie
- Physical and Theoretical Chemical Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ, U.K
| | - Hugh G A Burton
- Physical and Theoretical Chemical Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ, U.K
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15
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Xie Z, Song Y, Peng F, Li J, Cheng Y, Zhang L, Ma Y, Tian Y, Luo Z, Ma H. Kylin 1.0: An ab-initio density matrix renormalization group quantum chemistry program. J Comput Chem 2023; 44:1316-1328. [PMID: 36809661 DOI: 10.1002/jcc.27085] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 01/15/2023] [Accepted: 01/19/2023] [Indexed: 02/23/2023]
Abstract
The accurate evaluation of electron correlations is highly necessary for the proper descriptions of the electronic structures in strongly correlated molecules, ranging from bond-dissociating molecules, polyradicals, to large conjugated molecules and transition metal complexes. For this purpose, in this paper, a new ab-initio quantum chemistry program Kylin 1.0 for electron correlation calculations at various quantum many-body levels, including configuration interaction (CI), perturbation theory (PT), and density matrix renormalization group (DMRG), is presented. Furthermore, fundamental quantum chemistry methods such as Hartree-Fock self-consistent field (HF-SCF) and the complete active space SCF (CASSCF) are also implemented. The Kylin 1.0 program possesses the following features: (1) a matrix product operator (MPO) formulation-based efficient DMRG implementation for describing static electron correlation within a large active space composed of more than 100 orbitals, supporting both U 1 n × U 1 S z $$ \mathrm{U}{(1)}_{\mathrm{n}}\times \mathrm{U}{(1)}_{{\mathrm{S}}_{\mathrm{z}}} $$ and U 1 n × SU 2 S $$ \mathrm{U}{(1)}_{\mathrm{n}}\times \mathrm{SU}{(2)}_{\mathrm{S}} $$ symmetries; (2) an efficient second-order DMRG-self-consistent field (SCF) implementation; (3) an externally contracted multi-reference CI (MRCI) and Epstein-Nesbet PT with DMRG reference wave functions for including the remaining dynamic electron correlation outside the large active spaces. In this paper, we introduce the capabilities and numerical benchmark examples of the Kylin 1.0 program.
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Affiliation(s)
- Zhaoxuan Xie
- School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China
| | - Yinxuan Song
- School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China
| | - Fangwen Peng
- School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China
| | - Jianhao Li
- School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China
| | - Yifan Cheng
- School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China
| | - Lingzhi Zhang
- School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China
| | - Yingjin Ma
- Computer Network Information Center, Chinese Academy of Sciences, Beijing, China
| | - Yingqi Tian
- School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China
| | - Zhen Luo
- School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China
| | - Haibo Ma
- School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China.,Qingdao Institute for Theoretical and Computational Sciences, Qingdao Institute of Frontier and Interdisciplinary Science, Shandong University, Qingdao, China
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16
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Feldmann R, Baiardi A, Reiher M. Second-Order Self-Consistent Field Algorithms: From Classical to Quantum Nuclei. J Chem Theory Comput 2023; 19:856-873. [PMID: 36701300 DOI: 10.1021/acs.jctc.2c01035] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
This work presents a general framework for deriving exact and approximate Newton self-consistent field (SCF) orbital optimization algorithms by leveraging concepts borrowed from differential geometry. Within this framework, we extend the augmented Roothaan-Hall (ARH) algorithm to unrestricted electronic and nuclear-electronic calculations. We demonstrate that ARH yields an excellent compromise between stability and computational cost for SCF problems that are hard to converge with conventional first-order optimization strategies. In the electronic case, we show that ARH overcomes the slow convergence of orbitals in strongly correlated molecules with the example of several iron-sulfur clusters. For nuclear-electronic calculations, ARH significantly enhances the convergence already for small molecules, as demonstrated for a series of protonated water clusters.
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Affiliation(s)
- Robin Feldmann
- ETH Zürich, Laboratorium für Physikalische Chemie, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - Alberto Baiardi
- ETH Zürich, Laboratorium für Physikalische Chemie, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - Markus Reiher
- ETH Zürich, Laboratorium für Physikalische Chemie, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
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17
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Soto J. Photochemistry of 1-Phenyl-1-diazopropane and Its Diazirine Isomer: A CASSCF and MS-CASPT2 Study. J Phys Chem A 2022; 126:8372-8379. [DOI: 10.1021/acs.jpca.2c04816] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Juan Soto
- Department of Physical Chemistry, Faculty of Science, University of Málaga, 29071 Málaga, Spain
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18
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Yu C, Xiao Z, Chu W, Zhang Q, Chen Y, Zhao D. High-Resolution Electronic Spectrum of the 1,4,6-Heptatrienyl Radical in the Gas Phase. J Phys Chem A 2022; 126:8398-8403. [DOI: 10.1021/acs.jpca.2c05596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Chunting Yu
- Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, People’s Republic of China
| | - Zengjun Xiao
- Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, People’s Republic of China
| | - Wangyou Chu
- Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, People’s Republic of China
| | - Qiang Zhang
- Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, People’s Republic of China
| | - Yang Chen
- Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, People’s Republic of China
| | - Dongfeng Zhao
- Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, People’s Republic of China
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19
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Hanscam R, Neuscamman E. Applying Generalized Variational Principles to Excited-State-Specific Complete Active Space Self-consistent Field Theory. J Chem Theory Comput 2022; 18:6608-6621. [PMID: 36215108 DOI: 10.1021/acs.jctc.2c00639] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We employ a generalized variational principle to improve the stability, reliability, and precision of fully excited-state-specific complete active space self-consistent field theory. Compared to previous approaches that similarly seek to tailor this ansatz's orbitals and configuration interaction expansion for an individual excited state, we find the present approach to be more resistant to root flipping and better at achieving tight convergence to an energy stationary point. Unlike state-averaging, this approach allows orbital shapes to be optimal for individual excited states, which is especially important for charge-transfer states and some doubly excited states. We demonstrate the convergence and state-targeting abilities of this method in LiH, ozone, and MgO, showing in the latter that it is capable of finding three excited-state energy stationary points that no previous method has been able to locate.
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Affiliation(s)
- Rebecca Hanscam
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Eric Neuscamman
- Department of Chemistry, University of California, Berkeley, California 94720, United States.,Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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20
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Wang Z, Head-Gordon M. A linear surrogate for optimising functions of an orthogonal matrix with applications in wave function theory. Mol Phys 2022. [DOI: 10.1080/00268976.2022.2118185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Affiliation(s)
- Zhenling Wang
- Department of Chemistry, University of California, Berkeley, CA, USA
| | - Martin Head-Gordon
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
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21
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Chaussy L, Hagebaum-Reignier D, Humbel S, Nava P. Accurate computed singlet-triplet energy differences for cobalt systems: implication for two-state reactivity. Phys Chem Chem Phys 2022; 24:21841-21852. [PMID: 36065755 DOI: 10.1039/d2cp03291k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Accurate singlet-triplet energy differences for cobalt and rhodium complexes were calculated by using several wave function methods, such as MRCISD, CASPT2, CCSD(T) and BCCD(T). Relaxed energy differences were obtained by considering the singlet and triplet complexes, each at the minimum of their potential energy surfaces. Active spaces for multireference calculations were carefully checked to provide accurate results. The considered systems are built by increasing progressively the first coordination sphere around the metal. We included in our set two CpCoX complexes (Cp = cyclopentadienyl, X = alkenyl ligand), which have been suggested as intermediates in cycloaddition reactions. Indeed, cobalt systems have been used for more than a decade as active species in this kind of transformations, for which a two-state reactivity has been proposed. Most of the considered systems display a triplet ground state. However, in the case of a reaction intermediate, while a triplet ground state was predicted on the basis of Density Functional Theory results, our calculations suggest a singlet ground state. This stems from the competition between the exchange term (stabilising the triplet) and the accessibility of an intramolecular coordination (stabilising the singlet). This finding has an impact on the general mechanism of the cycloaddition reaction. Analogous rhodium systems were also studied and, as expected, they have a larger tendency to electron pairing than cobalt species.
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Affiliation(s)
- Léo Chaussy
- Aix-Marseille Univ, CNRS, Centrale Marseille, iSm2, Marseille, France.
| | | | - Stéphane Humbel
- Aix-Marseille Univ, CNRS, Centrale Marseille, iSm2, Marseille, France.
| | - Paola Nava
- Aix-Marseille Univ, CNRS, Centrale Marseille, iSm2, Marseille, France.
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22
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Smith JET, Lee J, Sharma S. Near-Exact Nuclear Gradients of Complete Active Space Self-Consistent Field Wave Functions. J Chem Phys 2022; 157:094104. [DOI: 10.1063/5.0085515] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
In this paper, we study the nuclear gradients of heat bath configuration interaction self-consistent field (HCISCF) wave functions and use them to optimize molecular geometries for various molecules.We show that the HCISCF nuclear gradients are fairly insensitive to the size of the "selected" variational space, which allows us to reduce the computational cost without introducing significant error.The ability of HCISCF to treat larger active spaces combined with the flexibility for users to control the computational cost makes the method very attractive for studying strongly correlated systems which require a larger active space than possible with complete active space self-consistent field (CASSCF).Finally, we study the realistic catalyst, Fe(PDI), and highlight some of the challenges this system poses for density functional theory (DFT).We demonstrate how HCISCF can clarify the energetic stability of geometries obtained from DFT when the results are strongly dependent on the functional.We also use the HCISCF gradients to optimize geometries for this species and study the adiabatic singlet-triplet gap. During geometry optimization, we find that multiple near-degenerate local minima exist on the triplet potential energy surface.
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Affiliation(s)
- James E. T. Smith
- Center for Computational Quantum Phyics, Flatiron Institute, United States of America
| | - Joonho Lee
- Chemistry, Columbia University Department of Chemistry, United States of America
| | - Sandeep Sharma
- University of Colorado at Boulder, United States of America
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23
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Kreplin DA, Werner HJ. A combined first- and second-order optimization method for improving convergence of Hartree–Fock and Kohn–Sham calculations. J Chem Phys 2022; 156:214111. [DOI: 10.1063/5.0094292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In this work, we investigate the optimization of Hartree–Fock (HF) orbitals with our recently proposed combined first- and second-order (SO-SCI) method, which was originally developed for multi-configuration self-consistent field (MCSCF) and complete active space SCF (CASSCF) calculations. In MCSCF/CASSCF, it unites a second-order optimization of the active orbitals with a Fock-based first-order treatment of the remaining closed-virtual orbital rotations. In the case of the single-determinant wavefunctions, the active space is replaced by a preselected “second-order domain,” and all rotations involving orbitals in this subspace are treated at second-order. The method has been implemented for spin-restricted and spin-unrestricted Hartree–Fock (RHF, UHF), configuration-averaged Hartree–Fock (CAHF), as well as Kohn–Sham (KS) density functional theory (RKS, UKS). For each of these cases, various choices of the second-order domain have been tested, and appropriate defaults are proposed. The performance of the method is demonstrated for several transition metal complexes. It is shown that the SO-SCI optimization provides faster and more robust convergence than the standard SCF procedure but requires, in many cases, even less computation time. In difficult cases, the SO-SCI method not only speeds up convergence but also avoids convergence to saddle-points. Furthermore, it helps to find spin-symmetry broken solutions in the cases of UHF or UKS. In the case of CAHF, convergence can also be significantly improved as compared to a previous SCF implementation. This is particularly important for multi-center cases with two or more equal heavy atoms. The performance is demonstrated for various two-center complexes with different lanthanide atoms.
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Affiliation(s)
- David A. Kreplin
- Institut für Theoretische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
| | - Hans-Joachim Werner
- Institut für Theoretische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
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24
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Salta Z, Vega-Teijido M, Katz A, Tasinato N, Barone V, Ventura ON. Dipolar 1,3-cycloaddition of thioformaldehyde S-methylide (CH 2 SCH 2 ) to ethylene and acetylene. A comparison with (valence) isoelectronic O 3 , SO 2 , CH 2 OO and CH 2 SO. J Comput Chem 2022; 43:1420-1433. [PMID: 35662073 DOI: 10.1002/jcc.26946] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 05/17/2022] [Accepted: 05/17/2022] [Indexed: 11/08/2022]
Abstract
Methods rooted in the density functional theory and in the coupled cluster ansatz were employed to investigate the cycloaddition reactions to ethylene and acetylene of 1,3-dipolar species including ozone and the derivatives issued from replacement of the central oxygen atom by the valence-isoelectronic sulfur atom, and/or of one or both terminal oxygen atoms by the isoelectronic CH2 group. This gives rise to five different 1,3-dipolar compounds, namely ozone itself (O3 ), sulfur dioxide (SO2 ), the simplest Criegee intermediate (CH2 OO), sulfine (CH2 SO), and thioformaldehyde S-methylide (CH2 SCH2 , TSM). The experimental and accurate theoretical data available for some of those molecules were employed to assess the accuracy of two last-generation composite methods employing conventional or explicitly correlated post-Hartree-Fock contributions (jun-Cheap and SVECV-f12, respectively), which were then applied to investigate the reactivity of TSM. The energy barriers provided by both composite methods are very close (the average values for the two composite methods are 7.1 and 8.3 kcal mol-1 for the addition to ethylene and acetylene, respectively) and comparable to those ruling the corresponding additions of ozone (4.0 and 7.7 kcal mol-1 , respectively). These and other evidences strongly suggest that, at least in the case of cycloadditions, the reactivity of TSM is similar to that of O3 and very different from that of SO2 .
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Affiliation(s)
- Zoi Salta
- SMART Lab, Scuola Normale Superiore, Pisa, Italy
| | - Mauricio Vega-Teijido
- Computational Chemistry and Biology Group, CCBG, DETEMA, Facultad de Química, Universidad de la República, Montevideo, Uruguay
| | - Aline Katz
- Computational Chemistry and Biology Group, CCBG, DETEMA, Facultad de Química, Universidad de la República, Montevideo, Uruguay
| | | | | | - Oscar N Ventura
- Computational Chemistry and Biology Group, CCBG, DETEMA, Facultad de Química, Universidad de la República, Montevideo, Uruguay
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25
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Helmich-Paris B. A trust-region augmented Hessian implementation for state-specific and state-averaged CASSCF wave functions. J Chem Phys 2022; 156:204104. [DOI: 10.1063/5.0090447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In this work, we present a one-step second-order converger for state-specific (SS) and state-averaged (SA) complete active space self-consistent field (CASSCF) wave functions. Robust convergence is achieved through step restrictions using a trust-region augmented Hessian (TRAH) algorithm. To avoid numerical instabilities, an exponential parameterization of variational configuration parameters is employed, which works with a nonredundant orthogonal complement basis. This is a common approach for SS-CASSCF and is extended to SA-CASSCF wave functions in this work. Our implementation is integral direct and based on intermediates that are formulated in either the sparse atomic-orbital or small active molecular-orbital basis. Thus, it benefits from a combination with efficient integral decomposition techniques, such as the resolution-of-the-identity or the chain-of-spheres for exchange approximations. This facilitates calculations on large molecules, such as a Ni(II) complex with 231 atoms and 5154 basis functions. The runtime performance of TRAH-CASSCF is competitive with the other state-of-the-art implementations of approximate and full second-order algorithms. In comparison with a sophisticated first-order converger, TRAH-CASSCF calculations usually take more iterations to reach convergence and, thus, have longer runtimes. However, TRAH-CASSCF calculations still converge reliably to a true minimum even if the first-order algorithm fails.
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Affiliation(s)
- Benjamin Helmich-Paris
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
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26
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Patra S, San Vicente Veliz JC, Koner D, Bieske EJ, Meuwly M. Photodissociation dynamics of N3+. J Chem Phys 2022; 156:124307. [DOI: 10.1063/5.0085081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The photodissociation dynamics of [Formula: see text] excited from its (linear) 3[Formula: see text]/(bent) 3A″ ground to the first excited singlet and triplet states is investigated. Three-dimensional potential energy surfaces for the 1A′, 1A″, and 3A′ electronic states, correlating with the 1Δg and 3Πu states in linear geometry, for [Formula: see text] are constructed using high-level electronic structure calculations and represented as reproducing kernels. The reference ab initio energies are calculated at the MRCI+Q/aug-cc-pVTZ level of theory. For following the photodissociation dynamics in the excited states, rotational and vibrational distributions P( v′) and P( j′) for the N2 product are determined from vertically excited ground state distributions. Due to the different shapes of the ground state 3A″ potential energy surface and the excited states, appreciable angular momentum j′ ∼ 60 is generated in diatomic fragments. The lifetimes in the excited states extend to at least 50 ps. Notably, results from sampling initial conditions from a thermal ensemble and from the Wigner distribution of the ground state wavefunction are comparable.
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Affiliation(s)
- Sarbani Patra
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
| | | | - Debasish Koner
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Tirupati, Karakambadi Road, Mangalam, Tirupati 517507, Andhra Pradesh, India
| | - Evan J. Bieske
- Department of Chemistry, University of Melbourne, Parkville 3010, Australia
| | - Markus Meuwly
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
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27
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Nishio S, Kurashige Y. Importance of dynamical electron correlation in diabatic couplings of electron-exchange processes. J Chem Phys 2022; 156:114107. [PMID: 35317578 DOI: 10.1063/5.0075978] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We demonstrate the importance of the dynamical electron correlation effect in diabatic couplings of electron-exchange processes in molecular aggregates. To perform a multireference perturbation theory with large active space of molecular aggregates, an efficient low-rank approximation is applied to the complete active space self-consistent field reference functions. It is known that kinetic rates of electron-exchange processes, such as singlet fission, triplet-triplet annihilation, and triplet exciton transfer, are not sufficiently explained by the direct term of the diabatic couplings but efficiently mediated by the low-lying charge transfer states if the two molecules are in close proximity. It is presented in this paper, however, that regardless of the distance of the molecules, the direct term is considerably underestimated by up to three orders of magnitude without the dynamical electron correlation, i.e., the diabatic states expressed in the active space are not adequate to quantitatively reproduce the electron-exchange processes.
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Affiliation(s)
- Soichiro Nishio
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Yuki Kurashige
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
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28
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Song C. State-averaged CASSCF with polarizable continuum model for studying photoreactions in solvents: Energies, analytical nuclear gradients, and non-adiabatic couplings. J Chem Phys 2022; 156:104102. [DOI: 10.1063/5.0085855] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
This paper presents state-averaged complete active space self-consistent field in polarizable continuum model (PCM) for studies of photoreactions in solvents. The wavefunctions of the solute and the PCM surface charges of the solvent are optimized simultaneously such that the state-averaged free energy is variationally minimized. The method supports both fixed weights and dynamic weights where the weights are automatically adjusted based on the energy gaps. The corresponding analytical nuclear gradients and non-adiabatic couplings are also derived. Furthermore, we show how the new method can be entirely formulated in terms of seven basic operations, which allows the implementation to benefit from existing high-performance libraries on graphical processing units. Results demonstrating the accuracy and performance of the implementation are presented and discussed. We also apply the new method to the study of minimal conical intersection search and photoreaction energy pathways in solvents. Effects from the polarity of the solvents and different formulas of dynamic weights are compared and discussed.
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Affiliation(s)
- Chenchen Song
- Department of Chemistry, University of California Davis, Davis, California 95616, USA
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29
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Pokhilko P, Yeh CN, Zgid D. Iterative subspace algorithms for finite-temperature solution of Dyson equation. J Chem Phys 2022; 156:094101. [DOI: 10.1063/5.0082586] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
One-particle Green’s functions obtained from the self-consistent solution of the Dyson equation can be employed in the evaluation of spectroscopic and thermodynamic properties for both molecules and solids. However, typical acceleration techniques used in the traditional quantum chemistry self-consistent algorithms cannot be easily deployed for the Green’s function methods because of a non-convex grand potential functional and a non-idempotent density matrix. Moreover, the optimization problem can become more challenging due to the inclusion of correlation effects, changing chemical potential, and fluctuations of the number of particles. In this paper, we study acceleration techniques to target the self-consistent solution of the Dyson equation directly. We use the direct inversion in the iterative subspace (DIIS), the least-squared commutator in the iterative subspace (LCIIS), and the Krylov space accelerated inexact Newton method (KAIN). We observe that the definition of the residual has a significant impact on the convergence of the iterative procedure. Based on the Dyson equation, we generalize the concept of the commutator residual used in DIIS and LCIIS and compare it with the difference residual used in DIIS and KAIN. The commutator residuals outperform the difference residuals for all considered molecular and solid systems within both GW and GF2. For a number of bond-breaking problems, we found that an easily obtained high-temperature solution with effectively suppressed correlations is a very effective starting point for reaching convergence of the problematic low-temperature solutions through a sequential reduction of temperature during calculations.
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Affiliation(s)
- Pavel Pokhilko
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Chia-Nan Yeh
- Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Dominika Zgid
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
- Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA
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30
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Soto J, Algarra M, Peláez D. Nitrene formation is the first step of the thermal and photochemical decomposition reactions of organic azides. Phys Chem Chem Phys 2022; 24:5109-5115. [PMID: 35156109 DOI: 10.1039/d1cp05785e] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
In this work, the decomposition of a prototypical azide, isopropyl azide, both in the ground and excited states, has been investigated through the use of multiconfigurational CASSCF and MS-CASPT2 electronic structure approaches. Particular emphasis has been placed on the thermal reaction starting at the S0 ground state surface. It has been found that the azide thermally decomposes via a stepwise mechanism, whose rate-determining step is the formation of isopropyl nitrene, which is, in turn, the first step of the global mechanism. After that, the nitrene isomerizes to the corresponding imine derivative. Two routes are possible for such a decomposition: (i) a spin-allowed path involving a transition state; and (ii) a spin-forbidden one via a S0/T0 intersystem crossing. Both intermediates have been determined and characterised. Their associated relative energies have been found to be quite similar, 45.75 and 45.52 kcal mol-1, respectively. To complete this study, the kinetics of the singlet and triplet channels are modeled with the MESMER (Master Equation Solver for Multi-Energy Well Reactions) code by applying the RRKM and Landau-Zener (with WKB tunnelling correction) theories, respectively. It is found that the canonical rate-coefficients of the singlet path are 2-orders of magnitude higher than the rate-coefficients of the forbidden reaction. In addition, the concerted mechanism has been investigated that would lead to the formation of the imine derivative and nitrogen extrusion in the first step of the decomposition. After a careful analysis of CASSCF calculations with different active spaces and their comparison with single electronic configuration methods (MP2 and B3LYP), the concerted mechanism is discarded.
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Affiliation(s)
- Juan Soto
- Department of Physical Chemistry, Faculty of Science, University of Málaga, E-29071 Málaga, Spain.
| | - Manuel Algarra
- INAMAT2 Institute for Advanced Materials and Mathematics, Department of Sciences, Campus de Arrosadia, 31006 Pamplona, Spain
| | - Daniel Peláez
- Institut des Sciences Moléculaires d'Orsay (ISMO) - UMR 8214, Université Paris-Saclay, 91405 Orsay Cedex, Spain
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31
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Guo Y, Zhang N, Lei Y, Liu W. iCISCF: An Iterative Configuration Interaction-Based Multiconfigurational Self-Consistent Field Theory for Large Active Spaces. J Chem Theory Comput 2021; 17:7545-7561. [PMID: 34757746 DOI: 10.1021/acs.jctc.1c00781] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
An iterative configuration interaction (iCI)-based multiconfigurational self-consistent field (SCF) theory, iCISCF, is proposed to handle systems that require large active spaces. The success of iCISCF stems from three ingredients: (1) efficient selection of individual configuration state functions spanning the active space while maintaining full spin symmetry; (2) the use of Jacobi rotation for optimization of the active orbitals in conjunction with a quasi-Newton algorithm for the core/active-virtual and core-active orbital rotations; (3) a second-order perturbative treatment of the residual space left over by the selection procedure (i.e., iCISCF(2)). Several examples that go beyond the capability of CASSCF are taken as showcases to reveal the efficacy of iCISCF and iCISCF(2), facilitated by iCAS for imposed automatic selection and localization of active orbitals.
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Affiliation(s)
- Yang Guo
- Qingdao Institute for Theoretical and Computational Sciences, Institute of Frontier and Interdisciplinary Science, Shandong University, Qingdao, Shandong 266237, China
| | - Ning Zhang
- Beijing National Laboratory for Molecular Sciences, Institute of Theoretical and Computational Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Yibo Lei
- Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry and Materials Science, Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Northwest University, Xi'an, Shaanxi 710127, China
| | - Wenjian Liu
- Qingdao Institute for Theoretical and Computational Sciences, Institute of Frontier and Interdisciplinary Science, Shandong University, Qingdao, Shandong 266237, China
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32
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Nottoli T, Gauss J, Lipparini F. Second-Order CASSCF Algorithm with the Cholesky Decomposition of the Two-Electron Integrals. J Chem Theory Comput 2021; 17:6819-6831. [PMID: 34719925 PMCID: PMC8582256 DOI: 10.1021/acs.jctc.1c00327] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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In this contribution,
we present the implementation of a second-order
complete active space–self-consistent field (CASSCF) algorithm
in conjunction with the Cholesky decomposition of the two-electron
repulsion integrals. The algorithm, called norm-extended optimization,
guarantees convergence of the optimization, but it involves the full
Hessian and is therefore computationally expensive. Coupling the second-order
procedure with the Cholesky decomposition leads to a significant reduction
in the computational cost, reduced memory requirements, and an improved
parallel performance. As a result, CASSCF calculations of larger molecular
systems become possible as a routine task. The performance of the
new implementation is illustrated by means of benchmark calculations
on molecules of increasing size, with up to about 3000 basis functions
and 14 active orbitals.
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Affiliation(s)
- Tommaso Nottoli
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa. Via G. Moruzzi 13, I-56124 Pisa, Italy
| | - Jürgen Gauss
- Department Chemie, Johannes Gutenberg-Universität Mainz, Duesbergweg 10-14, D-55128 Mainz, Germany
| | - Filippo Lipparini
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa. Via G. Moruzzi 13, I-56124 Pisa, Italy
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33
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Soto J, Algarra M. Electronic Structure of Nitrobenzene: A Benchmark Example of the Accuracy of the Multi-State CASPT2 Theory. J Phys Chem A 2021; 125:9431-9437. [PMID: 34677962 PMCID: PMC8573753 DOI: 10.1021/acs.jpca.1c04595] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
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The electronic structure
of nitrobenzene (C6H5NO2) has been
studied by means of the complete active
space self-consistent field (CASSCF) and multi-state second-order
perturbation (MS-CASPT2) methods. To this end, an active space of
20 electrons distributed in 17 orbitals has been selected to construct
the reference wave function. In this work, we have calculated the
vertical excitation energies and the energy barrier for the dissociation
of the molecule on the ground state into phenyl and nitrogen dioxide.
After applying the corresponding vibrational corrections to the electronic
energies, it is demonstrated that the MS-CASPT2//CASSCF values obtained
in this work yield an excellent agreement between calculated and experimental
data. In addition, other active spaces of lower size have been applied
to the system in order to check the active space dependence in the
results.
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Affiliation(s)
- Juan Soto
- Department of Physical Chemistry, Faculty of Science, University of Málaga, Málaga 29071, Spain
| | - Manuel Algarra
- Department of Inorganic Chemistry, Faculty of Science, University of Málaga, Málaga 29071, Spain
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34
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Mitrushchenkov AO, Zanchet A, Hauser AW, de Lara-Castells MP. Nonadiabatic Effects in the Molecular Oxidation of Subnanometric Cu 5 Clusters. J Phys Chem A 2021; 125:9143-9150. [PMID: 34633823 PMCID: PMC8543446 DOI: 10.1021/acs.jpca.1c07271] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
The electronic structure
of subnanometric clusters, far off the
bulk regime, is still dominated by molecular characteristics. The
spatial arrangement of the notoriously undercoordinated metal atoms
is strongly coupled to the electronic properties of the system, which
makes this class of materials particularly interesting for applications
including luminescence, sensing, bioimaging, theranostics, energy
conversion, catalysis, and photocatalysis. Opposing a common rule
of thumb that assumes an increasing chemical reactivity with smaller
cluster size, Cu5 clusters have proven to be exceptionally
resistant to irreversible oxidation, i.e., the dissociative chemisorption
of molecular oxygen. Besides providing reasons for this behavior in
the case of heavy loading with molecular oxygen, we investigate the
competition between physisorption and molecular chemisorption from
the perspective of nonadiabatic effects. Landau–Zener theory
is applied to the Cu5(O2)3 complex
to estimate the probability for a switching between the electronic
states correlating the neutral O2 + Cu5(O2)2 and the ionic O2– + (Cu5(O2)2)+ fragments in a diabatic representation.
Our work demonstrates the involvement of strong nonadiabatic effects
in the associated charge transfer process, which might be a common
motive in reactions involving subnanometric metal structures.
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Affiliation(s)
| | - Alexandre Zanchet
- Instituto de Física Fundamental (AbinitSim Unit), CSIC, Serrano 123, 28006 Madrid, Spain
| | - Andreas W Hauser
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria
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35
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Chen J, Berndt T, Møller KH, Lane JR, Kjaergaard HG. Atmospheric Fate of the CH 3SOO Radical from the CH 3S + O 2 Equilibrium. J Phys Chem A 2021; 125:8933-8941. [PMID: 34601880 DOI: 10.1021/acs.jpca.1c06900] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The atmospheric oxidation mechanisms of reduced sulfur compounds are of great importance in the biogeochemical sulfur cycle. The CH3S radical represents an important intermediate in these oxidation processes. Under atmospheric conditions, CH3S will predominantly react with O2 to form the peroxy radical CH3SOO. The formed CH3SOO has two competing unimolecular reaction pathways: isomerization to CH3SO2, which further decomposes into CH3 and SO2, or a hydrogen shift followed by HO2 loss, leading to CH2S. Previous theoretical calculations have suggested that CH2S formation should be the dominant pathway, in disagreement with existing experimental results. Our large active space multireference configuration interaction calculations agree with the experimental results that the formation of CH3 and SO2 is the dominant route and the formation of CH2S and HO2 can, at most, be a minor pathway. We support the calculations with new experiments starting from the OH + CH3SH reaction for CH3S formation under low NOx conditions and find a SO2 yield of 0.86 ± 0.18 within our reaction time of 7.9 s. Model simulations of our experiments show that the SO2 yield converges to 0.98. This combined theoretical and experimental study thus furthers the understanding of the general oxidation mechanisms of sulfur compounds in the atmosphere.
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Affiliation(s)
- Jing Chen
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
| | - Torsten Berndt
- Atmospheric Chemistry Department, Leibniz Institute for Tropospheric Research, Permoserstraße. 15, 04318 Leipzig, Germany
| | - Kristian H Møller
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
| | - Joseph R Lane
- School of Science, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand
| | - Henrik G Kjaergaard
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
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36
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Damour Y, Véril M, Kossoski F, Caffarel M, Jacquemin D, Scemama A, Loos PF. Accurate full configuration interaction correlation energy estimates for five- and six-membered rings. J Chem Phys 2021; 155:134104. [PMID: 34624964 DOI: 10.1063/5.0065314] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Following our recent work on the benzene molecule [P.-F. Loos, Y. Damour, and A. Scemama, J. Chem. Phys. 153, 176101 (2020)], motivated by the blind challenge of Eriksen et al. [J. Phys. Chem. Lett. 11, 8922 (2020)] on the same system, we report accurate full configuration interaction (FCI) frozen-core correlation energy estimates for 12 five- and six-membered ring molecules (cyclopentadiene, furan, imidazole, pyrrole, thiophene, benzene, pyrazine, pyridazine, pyridine, pyrimidine, s-tetrazine, and s-triazine) in the standard correlation-consistent double-ζ Dunning basis set (cc-pVDZ). Our FCI correlation energy estimates, with an estimated error smaller than 1 millihartree, are based on energetically optimized-orbital selected configuration interaction calculations performed with the configuration interaction using a perturbative selection made iteratively algorithm. Having at our disposal these accurate reference energies, the respective performance and convergence properties of several popular and widely used families of single-reference quantum chemistry methods are investigated. In particular, we study the convergence properties of (i) the Møller-Plesset perturbation series up to fifth-order (MP2, MP3, MP4, and MP5), (ii) the iterative approximate coupled-cluster series CC2, CC3, and CC4, and (iii) the coupled-cluster series CCSD, CCSDT, and CCSDTQ. The performance of the ground-state gold standard CCSD(T) as well as the completely renormalized CC model, CR-CC(2,3), is also investigated. We show that MP4 provides an interesting accuracy/cost ratio, while MP5 systematically worsens the correlation energy estimates. In addition, CC3 outperforms CCSD(T) and CR-CC(2,3), as well as its more expensive parent CCSDT. A similar trend is observed for the methods including quadruple excitations, where the CC4 model is shown to be slightly more accurate than CCSDTQ, both methods providing correlation energies within 2 millihartree of the FCI limit.
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Affiliation(s)
- Yann Damour
- Laboratoire de Chimie et Physique Quantiques (UMR 5626), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Mickaël Véril
- Laboratoire de Chimie et Physique Quantiques (UMR 5626), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Fábris Kossoski
- Laboratoire de Chimie et Physique Quantiques (UMR 5626), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Michel Caffarel
- Laboratoire de Chimie et Physique Quantiques (UMR 5626), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Denis Jacquemin
- Université de Nantes, CNRS, CEISAM UMR 6230, F-44000 Nantes, France
| | - Anthony Scemama
- Laboratoire de Chimie et Physique Quantiques (UMR 5626), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Pierre-François Loos
- Laboratoire de Chimie et Physique Quantiques (UMR 5626), Université de Toulouse, CNRS, UPS, Toulouse, France
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37
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Bhattacharya D, Shamasundar KR, Emmanouilidou A. Potential Energy Curves of Molecular Nitrogen for Singly and Doubly Ionized States with Core and Valence Holes. J Phys Chem A 2021; 125:7778-7787. [PMID: 34477371 DOI: 10.1021/acs.jpca.1c04613] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Theoretical description of potential energy curves (PECs) of molecular ions is essential for interpretation and prediction of coupled electron-nuclear dynamics following ionization of parent molecule. However, an accurate representation of these PECs for core or inner valence ionized state is nontrivial, especially at stretched geometries for double- or triple-bonded systems. In this work, we report PECs of singly and doubly ionized states of molecular nitrogen using state-of-the-art quantum chemical methods. The valence, inner valence, and core ionized states have been computed. A double-loop optimization scheme that separates the treatment of the core and the valence orbitals during the orbital optimization step of the multiconfiguration self-consistent field method has been implemented. This technique allows the energy to be converged to any desired ionized state with any number of core or inner-shell holes. The present work also compares the PECs obtained using both delocalized and localized sets of orbitals for the core hole states. The PECs of a number of singly and doubly ionized valence states have also been computed and compared with previous studies. The computed PECs reported here are expected to be of importance for future studies to understand the interplay between photoionization and Auger spectra during the breakup of molecular nitrogen when interacting with intense free electron lasers.
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Affiliation(s)
- Debarati Bhattacharya
- Department of Physics and Astrophysics, University College London, Gower Street, London WC1E 6BT, U.K
| | - K R Shamasundar
- Indian Institute of Science Education and Research, Mohali, Sector 81, SAS Nagar, Mohali 140306, India
| | - Agapi Emmanouilidou
- Department of Physics and Astrophysics, University College London, Gower Street, London WC1E 6BT, U.K
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38
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Dobrautz W, Weser O, Bogdanov NA, Alavi A, Li Manni G. Spin-Pure Stochastic-CASSCF via GUGA-FCIQMC Applied to Iron-Sulfur Clusters. J Chem Theory Comput 2021; 17:5684-5703. [PMID: 34469685 PMCID: PMC8444347 DOI: 10.1021/acs.jctc.1c00589] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Indexed: 11/28/2022]
Abstract
In this work, we demonstrate how to efficiently compute the one- and two-body reduced density matrices within the spin-adapted full configuration interaction quantum Monte Carlo (FCIQMC) method, which is based on the graphical unitary group approach (GUGA). This allows us to use GUGA-FCIQMC as a spin-pure configuration interaction (CI) eigensolver within the complete active space self-consistent field (CASSCF) procedure and hence to stochastically treat active spaces far larger than conventional CI solvers while variationally relaxing orbitals for specific spin-pure states. We apply the method to investigate the spin ladder in iron-sulfur dimer and tetramer model systems. We demonstrate the importance of the orbital relaxation by comparing the Heisenberg model magnetic coupling parameters from the CASSCF procedure to those from a CI-only (CASCI) procedure based on restricted open-shell Hartree-Fock orbitals. We show that the orbital relaxation differentially stabilizes the lower-spin states, thus enlarging the coupling parameters with respect to the values predicted by ignoring orbital relaxation effects. Moreover, we find that, while CASCI results are well fit by a simple bilinear Heisenberg Hamiltonian, the CASSCF eigenvalues exhibit deviations that necessitate the inclusion of biquadratic terms in the model Hamiltonian.
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Affiliation(s)
- Werner Dobrautz
- Max
Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
| | - Oskar Weser
- Max
Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
| | - Nikolay A. Bogdanov
- Max
Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
| | - Ali Alavi
- Max
Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Lensfield
Road, Cambridge CB2 1EW, United Kingdom
| | - Giovanni Li Manni
- Max
Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
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39
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Lei Y, Suo B, Liu W. iCAS: Imposed Automatic Selection and Localization of Complete Active Spaces. J Chem Theory Comput 2021; 17:4846-4859. [PMID: 34314180 DOI: 10.1021/acs.jctc.1c00456] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
It is shown that in the spirit of "from fragments to molecule" for localizing molecular orbitals [J. Chem. Theory Comput. 2011, 7, 3643], a prechosen set of occupied/virtual valence/core atomic/fragmental orbitals can be transformed to an equivalent set of localized occupied/virtual pre-localized molecular orbitals (pre-LMO), which can then be taken as probes to select the same number of maximally matching localized occupied/virtual Hartree-Fock (HF) or restricted open-shell HF (ROHF) molecular orbitals as the initial local orbitals spanning the desired complete active space (CAS). In each cycle of the self-consistent field (SCF) calculation, the CASSCF orbitals can be localized by means of the noniterative "top-down least-change" algorithm for localizing ROHF orbitals [J. Chem. Phys. 2017, 146, 104104] such that the maximum matching between the orbitals of two adjacent iterations can readily be monitored, leading finally to converged localized CASSCF orbitals that overlap most the guess orbitals. Such an approach is to be dubbed as "imposed CASSCF" (iCASSCF or simply iCAS in short) for good reasons: (1) it has been assumed that only those electronic states that have largest projections onto the active space defined by the prechosen atomic/fragmental orbitals are to be targeted. This is certainly an imposed constraint but has wide applications in organic and transition metal chemistry where valence (or core) atomic/fragmental orbitals can readily be identified. (2) The selection of both initial and optimized local active orbitals is imposed from the very beginning by the pre-LMOs (which span the same space as the prechosen atomic/fragmental orbitals). Apart from the (imposed) automation and localization, iCAS has two additional merits: (a) the guess orbitals are guaranteed to be the same for all geometries, for the pre-LMOs do not change in character with geometry and (b) the use of localized orbitals facilitates the SCF convergence, particularly for large active spaces. Both organic molecules and transition-metal complexes are taken as showcases to reveal the efficacy of iCAS.
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Affiliation(s)
- Yibo Lei
- Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education, College of Chemistry & Materials Science, Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Northwest University, Xi'an 710127, Shaanxi, P. R. China
| | - Bingbing Suo
- Institute of Modern Physics, Northwest University, and Shaanxi Key Laboratory for Theoretical Physics Frontiers, Xi'an 710127, Shaanxi, P. R. China
| | - Wenjian Liu
- Qingdao Institute for Theoretical and Computational Sciences, Institute of Frontier and Interdisciplinary Science, Shandong University, Qingdao 266237, Shandong, P. R. China
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40
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Lemm D, von Rudorff GF, von Lilienfeld OA. Machine learning based energy-free structure predictions of molecules, transition states, and solids. Nat Commun 2021; 12:4468. [PMID: 34294693 PMCID: PMC8298673 DOI: 10.1038/s41467-021-24525-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 06/22/2021] [Indexed: 02/06/2023] Open
Abstract
The computational prediction of atomistic structure is a long-standing problem in physics, chemistry, materials, and biology. Conventionally, force-fields or ab initio methods determine structure through energy minimization, which is either approximate or computationally demanding. This accuracy/cost trade-off prohibits the generation of synthetic big data sets accounting for chemical space with atomistic detail. Exploiting implicit correlations among relaxed structures in training data sets, our machine learning model Graph-To-Structure (G2S) generalizes across compound space in order to infer interatomic distances for out-of-sample compounds, effectively enabling the direct reconstruction of coordinates, and thereby bypassing the conventional energy optimization task. The numerical evidence collected includes 3D coordinate predictions for organic molecules, transition states, and crystalline solids. G2S improves systematically with training set size, reaching mean absolute interatomic distance prediction errors of less than 0.2 Å for less than eight thousand training structures - on par or better than conventional structure generators. Applicability tests of G2S include successful predictions for systems which typically require manual intervention, improved initial guesses for subsequent conventional ab initio based relaxation, and input generation for subsequent use of structure based quantum machine learning models.
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Affiliation(s)
- Dominik Lemm
- Faculty of Physics, University of Vienna, Vienna, Austria
| | | | - O Anatole von Lilienfeld
- Faculty of Physics, University of Vienna, Vienna, Austria.
- Institute of Physical Chemistry and National Center for Computational Design and Discovery of Novel Materials (MARVEL), Department of Chemistry, University of Basel, Basel, Switzerland.
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41
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Yao Y, Umrigar CJ. Orbital Optimization in Selected Configuration Interaction Methods. J Chem Theory Comput 2021; 17:4183-4194. [PMID: 34132530 DOI: 10.1021/acs.jctc.1c00385] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We study several approaches to orbital optimization in selected configuration interaction (SCI) plus perturbation theory methods and test them on the ground and excited states of three molecules using the semistochastic heat-bath configuration interaction method. We discuss the ways in which the orbital optimization problem in SCI resembles and differs from that in complete active space self-consistent field. Starting from natural orbitals, these approaches divide into three classes of optimization methods according to how they treat coupling between configuration interaction coefficients and orbital parameters, namely uncoupled, fully coupled, and quasi-fully coupled methods. We demonstrate that taking the coupling into account is crucial for fast convergence and recommend two quasi-fully coupled methods for such applications: accelerated diagonal Newton and Broyden-Fletcher-Goldfarb-Shanno.
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Affiliation(s)
- Yuan Yao
- Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, United States
| | - C J Umrigar
- Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, United States
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42
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Santra G, Semidalas E, Martin JML. Exploring Avenues beyond Revised DSD Functionals: II. Random-Phase Approximation and Scaled MP3 Corrections. J Phys Chem A 2021; 125:4628-4638. [PMID: 34019413 PMCID: PMC8279643 DOI: 10.1021/acs.jpca.1c01295] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
![]()
For revDSD double
hybrids, the Görling–Levy second-order
perturbation theory component is an Achilles’ heel when applied
to systems with significant near-degeneracy (“static”)
correlation. We have explored its replacement by the direct random
phase approximation (dRPA), inspired by the SCS-dRPA75 functional
of Kállay and co-workers. The addition to the final energy
of both a D4 empirical dispersion correction and of a semilocal correlation
component lead to significant improvements, with DSD-PBEdRPA75-D4 approaching the performance of revDSD-PBEP86-D4 and the Berkeley
ωB97M(2). This form appears to be fairly insensitive to the
choice of the semilocal functional but does exhibit stronger basis
set sensitivity than the PT2-based double hybrids (due to much larger
prefactors for the nonlocal correlation). As an alternative, we explored
adding an MP3-like correction term (in a medium-sized basis set) to
a range-separated ωDSD-PBEP86-D4 double hybrid and found it
to have significantly lower WTMAD2 (weighted mean absolute deviation)
for the large and chemically diverse GMTKN55 benchmark suite; the
added computational cost can be mitigated through density fitting
techniques.
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Affiliation(s)
- Golokesh Santra
- Department of Organic Chemistry, Weizmann Institute of Science, 7610001 Reḥovot, Israel
| | - Emmanouil Semidalas
- Department of Organic Chemistry, Weizmann Institute of Science, 7610001 Reḥovot, Israel
| | - Jan M L Martin
- Department of Organic Chemistry, Weizmann Institute of Science, 7610001 Reḥovot, Israel
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43
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Santra G, Cho M, Martin JML. Exploring Avenues beyond Revised DSD Functionals: I. Range Separation, with xDSD as a Special Case. J Phys Chem A 2021; 125:4614-4627. [PMID: 34009986 PMCID: PMC8279641 DOI: 10.1021/acs.jpca.1c01294] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 05/06/2021] [Indexed: 01/16/2023]
Abstract
We have explored the use of range separation as a possible avenue for further improvement on our revDSD minimally empirical double hybrid functionals. Such ωDSD functionals encompass the XYG3 type of double hybrid (i.e., xDSD) as a special case for ω → 0. As in our previous studies, the large and chemically diverse GMTKN55 benchmark suite was used for evaluation. Especially when using the D4 rather than D3BJ dispersion model, xDSD has a slight performance advantage in WTMAD2. As in previous studies, PBEP86 is the winning combination for the semilocal parts. xDSDn-PBEP86-D4 marginally outperforms the previous "best in class" ωB97M(2) Berkeley double hybrid but without range separation and using fewer than half the number of empirical parameters. Range separation turns out to offer only marginal further improvements on GMTKN55 itself. While ωB97M(2) still yields better performance for small-molecule thermochemistry, this is compensated in WTMAD2 by the superior performance of the new functionals for conformer equilibria. Results for two external test sets with pronounced static correlation effects may indicate that range-separated double hybrids are more resilient to such effects.
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Affiliation(s)
- Golokesh Santra
- Department
of Organic Chemistry, Weizmann Institute
of Science, 7610001 Reḥovot, Israel
| | - Minsik Cho
- Department
of Organic Chemistry, Weizmann Institute
of Science, 7610001 Reḥovot, Israel
- Department
of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Jan M. L. Martin
- Department
of Organic Chemistry, Weizmann Institute
of Science, 7610001 Reḥovot, Israel
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44
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San Vicente Veliz JC, Koner D, Schwilk M, Bemish RJ, Meuwly M. The C( 3P) + O 2( 3Σ g-) → CO 2 ↔ CO( 1Σ +) + O( 1D)/O( 3P) reaction: thermal and vibrational relaxation rates from 15 K to 20 000 K. Phys Chem Chem Phys 2021; 23:11251-11263. [PMID: 33949507 PMCID: PMC8133592 DOI: 10.1039/d1cp01101d] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Thermal rates for the C(3P) + O2(3Σg−) ↔ CO(1Σ+)+ O(1D)/O(3P) reaction are investigated over a wide temperature range based on quasi classical trajectory (QCT) simulations on 3-dimensional, reactive potential energy surfaces (PESs) for the 1A′, (2)1A′, 1A′′, 3A′ and 3A′′ states. These five states are the energetically low-lying states of CO2 and their PESs are computed at the MRCISD+Q/aug-cc-pVTZ level of theory using a state-average CASSCF reference wave function. Analysis of the different electronic states for the CO2 → CO + O dissociation channel rationalizes the topography of this region of the PESs. The forward rates from QCT simulations match measurements between 15 K and 295 K whereas the equilibrium constant determined from the forward and reverse rates is consistent with that derived from statistical mechanics at high temperature. Vibrational relaxation, O + CO(ν = 1,2) → O + CO(ν = 0), is found to involve both, non-reactive and reactive processes. The contact time required for vibrational relaxation to take place is τ ≥ 150 fs for non-reacting and τ ≥ 330 fs for reacting (oxygen atom exchange) trajectories and the two processes are shown to probe different parts of the global potential energy surface. In agreement with experiments, low collision energy reactions for the C(3P) + O2(3Σg−, ν = 0) → CO(1Σ+) + O(1D) lead to CO(1Σ+, ν′ = 17) with an onset at Ec ∼ 0.15 eV, dominated by the 1A′ surface with contributions from the 3A′ surface. Finally, the barrier for the COA(1Σ+) + OB(3P) → COB(1Σ+) + OA(3P) atom exchange reaction on the 3A′ PES yields a barrier of ∼7 kcal mol−1 (0.300 eV), consistent with an experimentally reported value of 6.9 kcal mol−1 (0.299 eV). Reaction and vibrational relaxation rate computed for C(3P) + O2(3Σg−) ↔ CO(1Σ+) + O(1D)/O(3P) for a wide range of temperatures using quasiclassical trajectory calculations on five new potential energy surfaces for different electronic states.![]()
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Affiliation(s)
| | - Debasish Koner
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland.
| | - Max Schwilk
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland. and University of Vienna, Faculty of Physics, 1090 Vienna, Austria
| | - Raymond J Bemish
- Air Force Research Laboratory, Space Vehicles Directorate, Kirtland AFB, New Mexico 87117, USA
| | - Markus Meuwly
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland. and Brown University, Providence, RI 02912, USA
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45
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Park JW. Second-Order Orbital Optimization with Large Active Spaces Using Adaptive Sampling Configuration Interaction (ASCI) and Its Application to Molecular Geometry Optimization. J Chem Theory Comput 2021; 17:1522-1534. [DOI: 10.1021/acs.jctc.0c01292] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Jae Woo Park
- Department of Chemistry, Chungbuk National University (CBNU), Cheongju 28644, Korea
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46
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Fajen OJ, Brorsen KR. Multicomponent CASSCF Revisited: Large Active Spaces Are Needed for Qualitatively Accurate Protonic Densities. J Chem Theory Comput 2021; 17:965-974. [PMID: 33404241 DOI: 10.1021/acs.jctc.0c01191] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Multicomponent methods seek to treat select nuclei, typically protons, fully quantum mechanically and equivalent to the electrons of a chemical system. In such methods, it is well-known that due to the neglect of electron-proton correlation, a Hartree-Fock (HF) description of the electron-proton interaction catastrophically fails leading to qualitatively incorrect protonic properties. In single-component quantum chemistry, the qualitative failure of HF is normally indicative of the need for multireference methods such as complete active space self-consistent field (CASSCF). While a multicomponent CASSCF method was implemented nearly 20 years ago, it is only able to perform calculations with very small active spaces (∼105 multicomponent configurations). Therefore, in order to extend the realm of applicability of the multicomponent CASSCF method, this study derives and implements a new two-step multicomponent CASSCF method that uses multicomponent heat-bath configuration interaction for the configuration interaction step, enabling calculations with very large active spaces (up to 16 electrons in 48 orbitals). We find that large electronic active spaces are needed to obtain qualitatively accurate protonic densities for the HCN and FHF- molecules. Additionally, the multicomponent CASSCF method implemented here should have further applications for double-well protonic potentials and systems that are inherently electronically multireference.
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Affiliation(s)
- O Jonathan Fajen
- Department of Chemistry, University of Missouri, Columbia, Missouri 65203, United States
| | - Kurt R Brorsen
- Department of Chemistry, University of Missouri, Columbia, Missouri 65203, United States
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47
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Salta Z, Segovia ME, Katz A, Tasinato N, Barone V, Ventura ON. Isomerization and Fragmentation Reactions on the [C 2SH 4] Potential Energy Surface: The Metastable Thione S-Methylide Isomer. J Org Chem 2021; 86:2941-2956. [PMID: 33501826 PMCID: PMC8023414 DOI: 10.1021/acs.joc.0c02835] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Thione S-methylide, parent species of the thiocarbonyl ylide family, is a 1,3-dipolar species on the [C2SH4] potential energy surface, not so much studied as its isomers, thiirane, vinyl thiol, and thioacetaldehyde. The conrotatory ring-closure reaction toward thiirane was studied in the 90s, but no complete analysis of the potential energy surface is available. In this paper, we report a computational study of the reaction scheme linking all species. We employed several computational methods (density functional theory, CCSD(T) composite schemes, and CASSCF/CASPT2 multireference procedures) to find the best description of thione S-methylide, its isomers, and transition states. The barrier from thiirane to thione S-methylide amounts to 52.2 kcal mol-1 (against 17.6 kcal mol-1 for the direct one), explaining why thiocarbonyl ylides cannot be prepared from thiiranes. Conversion of thiirane to vinyl thiol implies a large barrier, supporting why the reaction has been observed only at high temperatures. Fragmentations of thiirane to S(3P) or S(1D) and ethylene as well as decomposition to hydrogen sulfide plus acetylene were also explored. Triplet and singlet open-shell species were identified as intermediates in the fragmentations, with energies lower than the transition state between thiirane and vinyl thiol, explaining the preference of the latter at low temperatures.
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Affiliation(s)
- Zoi Salta
- Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
| | - Marc E Segovia
- Computational Chemistry and Biology Group, CCBG, DETEMA, Facultad de Química, Universidad de la República, 11400 Montevideo, Uruguay
| | - Aline Katz
- Computational Chemistry and Biology Group, CCBG, DETEMA, Facultad de Química, Universidad de la República, 11400 Montevideo, Uruguay
| | - Nicola Tasinato
- Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
| | - Vincenzo Barone
- Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
| | - Oscar N Ventura
- Computational Chemistry and Biology Group, CCBG, DETEMA, Facultad de Química, Universidad de la República, 11400 Montevideo, Uruguay
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48
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Soto J, Peláez D, Otero JC. A SA-CASSCF and MS-CASPT2 study on the electronic structure of nitrosobenzene and its relation to its dissociation dynamics. J Chem Phys 2021; 154:044307. [PMID: 33514099 DOI: 10.1063/5.0033181] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The photodissociation channels of nitrosobenzene (PhNO) induced by a 255 nm photolytic wavelength have been studied using the complete active space self-consistent method and the multistate second-order multiconfigurational perturbation theory. It is found that there exists a triplet route for photodissociation of the molecule. The reaction mechanism consists of a complex cascade of nonadiabatic electronic transitions involving triple and double conical intersections as well as intersystem crossing. Several of the relevant states (S2, S4, and S5 states) correspond to double excitations. It is worth noting that the last step of the photodissociation implies an internal conversion process. The experimentally observed velocity pattern of the NO fragment is a signature of such a conical intersection.
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Affiliation(s)
- Juan Soto
- Department of Physical Chemistry, Faculty of Science, University of Málaga, Andalucía Tech., E-29071 Málaga, SpainInstitut des Sciences Moléculaires d'Orsay (ISMO) - UMR 8214, Université Paris-Saclay, 91405 Orsay Cedex, France
| | - Daniel Peláez
- Institut des Sciences Moléculaires d'Orsay (ISMO) - UMR 8214, Université Paris-Saclay, 91405 Orsay Cedex, France
| | - Juan C Otero
- Department of Physical Chemistry, Faculty of Science, University of Málaga, Andalucía Tech., E-29071 Málaga, Spain
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49
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Li Y, Lu J. Optimal Orbital Selection for Full Configuration Interaction (OptOrbFCI): Pursuing the Basis Set Limit under a Budget. J Chem Theory Comput 2020; 16:6207-6221. [DOI: 10.1021/acs.jctc.0c00613] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Yingzhou Li
- Department of Mathematics, Duke University, Durham, North Carolina 27708, United States
| | - Jianfeng Lu
- Department of Mathematics, Duke University, Durham, North Carolina 27708, United States
- Department of Chemistry and Department of Physics, Duke University, Durham, North Carolina 27708, United States
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50
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Koner D, Schwilk M, Patra S, Bieske EJ, Meuwly M. N3+: Full-dimensional ground state potential energy surface, vibrational energy levels, and dynamics. J Chem Phys 2020; 153:044302. [DOI: 10.1063/5.0011957] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Debasish Koner
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
| | - Max Schwilk
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
| | - Sarbani Patra
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
| | - Evan J. Bieske
- Department of Chemistry, University of Melbourne, Parkville 3010, Australia
| | - Markus Meuwly
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland
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