1
|
Kirkland JK, Kumawat J, Shaban Tameh M, Tolman T, Lambert AC, Lief GR, Yang Q, Ess DH. Machine Learning Models for Predicting Zirconocene Properties and Barriers. J Chem Inf Model 2024; 64:775-784. [PMID: 38259142 DOI: 10.1021/acs.jcim.3c01575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Zr metallocenes have significant potential to be highly tunable polyethylene catalysts through modification of the aromatic ligand framework. Here we report the development of multiple machine learning models using a large library (>700 systems) of DFT-calculated zirconocene properties and barriers for ethylene polymerization. We show that very accurate machine learning models are possible for HOMO-LUMO gaps of precatalysts but the performance significantly depends on the machine learning algorithm and type of featurization, such as fingerprints, Coulomb matrices, smooth overlap of atomic positions, or persistence images. Surprisingly, the description of the bonding hapticity, the number of direct connections between Zr and the ligand aromatic carbons, only has a moderate influence on the performance of most models. Despite robust models for HOMO-LUMO gaps, these types of machine learning models based on structure connectivity type features perform poorly in predicting ethylene migratory insertion barrier heights. Therefore, we developed several relatively robust and accurate machine learning models for barrier heights that are based on quantum-chemical descriptors (QCDs). The quantitative accuracy of these models depends on which potential energy surface structure QCDs were harvested from. This revealed a Hammett-type principle to naturally emerge showing that QCDs from the π-coordination complexes provide much better descriptions of the transition states than other potential-energy structures. Feature importance analysis of the QCDs provides several fundamental principles that influence zirconocene catalyst reactivity.
Collapse
Affiliation(s)
- Justin K Kirkland
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84604, United States
| | - Jugal Kumawat
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84604, United States
| | - Maliheh Shaban Tameh
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84604, United States
| | - Tyson Tolman
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84604, United States
| | - Allison C Lambert
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84604, United States
| | - Graham R Lief
- Research and Technology, Chevron Phillips Chemical Company, Highways 60 & 123, Bartlesville, Oklahoma 74003, United States
| | - Qing Yang
- Research and Technology, Chevron Phillips Chemical Company, Highways 60 & 123, Bartlesville, Oklahoma 74003, United States
| | - Daniel H Ess
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84604, United States
| |
Collapse
|
2
|
Dergachev VD, Nakritskaia DD, Alexeev Y, Gaita-Ariño A, Varganov SA. Analytical nonadiabatic coupling and state-specific energy gradient for the crystal field Hamiltonian describing lanthanide single-ion magnets. J Chem Phys 2023; 159:184111. [PMID: 37962443 DOI: 10.1063/5.0168996] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2023] [Accepted: 10/20/2023] [Indexed: 11/15/2023] Open
Abstract
Paramagnetic molecules with a metal ion as an electron spin center are promising building blocks for molecular qubits and high-density memory arrays. However, fast spin relaxation and decoherence in these molecules lead to a rapid loss of magnetization and quantum information. Nonadiabatic coupling (NAC), closely related to spin-vibrational coupling, is the main source of spin relaxation and decoherence in paramagnetic molecules at higher temperatures. Predicting these couplings using numerical differentiation requires a large number of computationally intensive ab initio or crystal field electronic structure calculations. To reduce computational cost and improve accuracy, we derive and implement analytical NAC and state-specific energy gradient for the ab initio parametrized crystal field Hamiltonian describing single-ion molecular magnets. Our implementation requires only a single crystal field calculation. In addition, the accurate NACs and state-specific energy gradients can be used to model spin relaxation using sophisticated nonadiabatic molecular dynamics, which avoids the harmonic approximation for molecular vibrations. To test our implementation, we calculate the NAC values for three lanthanide complexes. The predicted values support the relaxation mechanisms reported in previous studies.
Collapse
Affiliation(s)
- Vsevolod D Dergachev
- Department of Chemistry, University of Nevada, Reno, 1664 N. Virginia Street, Reno, Nevada 89557-0216, USA
| | - Daria D Nakritskaia
- Department of Chemistry, University of Nevada, Reno, 1664 N. Virginia Street, Reno, Nevada 89557-0216, USA
| | - Yuri Alexeev
- Computational Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
| | - Alejandro Gaita-Ariño
- Instituto de Ciencia Molecular (ICMol), Universidad de Valencia, c/Catedrático José Beltrán, 2, 46980 Paterna, Spain
| | - Sergey A Varganov
- Department of Chemistry, University of Nevada, Reno, 1664 N. Virginia Street, Reno, Nevada 89557-0216, USA
| |
Collapse
|
3
|
Dergachev ID, Dergachev VD, Rooein M, Mirzanejad A, Varganov SA. Predicting Kinetics and Dynamics of Spin-Dependent Processes. Acc Chem Res 2023; 56:856-866. [PMID: 36926853 DOI: 10.1021/acs.accounts.2c00843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/18/2023]
Abstract
ConspectusPredicting mechanisms and rates of nonadiabatic spin-dependent processes including photoinduced intersystem crossings, thermally activated spin-forbidden reactions, and spin crossovers in metal centers is a very active field of research. These processes play critical roles in transition-metal-based and metalloenzymatic catalysis, molecular magnets, light-harvesting materials, organic light-emitting diodes, photosensitizers for photodynamic therapy, and many other applications. Therefore, accurate modeling of spin-dependent processes in complex systems and on different time scales is important for many problems in chemistry, biochemistry, and materials sciences.Nonadiabatic statistical theory (NAST) and nonadiabatic molecular dynamics (NAMD) are two complementary approaches to modeling the kinetics and dynamics of spin-dependent processes. NAST predicts the probabilities and rate constants of nonradiative transitions between electronic states with different spin multiplicities using molecular properties at only few critical points on the potential energy surfaces (PESs), including the reactant minimum and the minimum energy crossing point (MECP) between two spin states. This makes it possible to obtain molecular properties for NAST calculations using accurate but often computationally expensive electronic structure methods, which is critical for predicting the rate constants of spin-dependent processes. Alternatively, NAST can be used to study spin-dependent processes in very large complex molecular systems using less computationally expensive electronic structure methods. The nuclear quantum effects, such as zero-point vibrational energy, tunneling, and interference between reaction paths can be easily incorporated. However, the statistical and local nature of NAST makes it more suitable for large systems and slow kinetics. In contrast, NAMD explores entire PESs of interacting electronic states, making it ideal for modeling fast barrierless spin-dependent processes. Because the knowledge of large portions of PESs is often needed, the simulations require a very large number of electronic structure calculations, which limits the NAMD applicability to relatively small molecular systems and ultrafast kinetics.In this Account, we discuss our contribution to the development of the NAST and NAMD approaches for predicting the rates and mechanism of spin-dependent processes. First, we briefly describe our NAST and NAMD implementations. The NAST implementation is an extension of the transition state theory to the processes involving two crossing potential energy surfaces of different spin multiplicities. The NAMD approach includes the trajectory surface hopping (TSH) and ab initio multiple spawning (AIMS) methods. Second, we discuss several applications of NAST and NAMD to model spin-dependent processes in different systems. The NAST applicability to large complex systems is demonstrated by the studies of the spin-forbidden isomerization of the active sites of metal-sulfur proteins. Our implementation of the MECP search algorithm within the fully ab initio fragment molecular orbital method allows applying NAST to systems with thousands of atoms, such as the solvated protein rubredoxin. Applications of NAMD to ultrafast spin-dependent processes are represented by the generalized AIMS simulations utilizing the fast GPU-based TeraChem electronic structure program to gain insight into the complex photoexcited state relaxation in 2-cyclopentenone.
Collapse
Affiliation(s)
- Ilya D Dergachev
- Department of Chemistry, University of Nevada, Reno, 1664 N. Virginia Street, Reno, Nevada 89557-0216, United States
| | - Vsevolod D Dergachev
- Department of Chemistry, University of Nevada, Reno, 1664 N. Virginia Street, Reno, Nevada 89557-0216, United States
| | - Mitra Rooein
- Department of Chemistry, University of Nevada, Reno, 1664 N. Virginia Street, Reno, Nevada 89557-0216, United States
| | - Amir Mirzanejad
- Department of Chemistry, University of Nevada, Reno, 1664 N. Virginia Street, Reno, Nevada 89557-0216, United States
| | - Sergey A Varganov
- Department of Chemistry, University of Nevada, Reno, 1664 N. Virginia Street, Reno, Nevada 89557-0216, United States
| |
Collapse
|
4
|
Komarov K, Park W, Lee S, Zeng T, Choi CH. Accurate Spin-Orbit Coupling by Relativistic Mixed-Reference Spin-Flip-TDDFT. J Chem Theory Comput 2023; 19:953-964. [PMID: 36655271 DOI: 10.1021/acs.jctc.2c01036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Relativistic mixed-reference spin-flip (MRSF)-TDDFT is developed considering the spin-orbit coupling (SOC) within the mean-field approximation. The resulting SOC-MRSF faithfully reproduces the experiments with very high accuracy, which is also consistent with the values by four-component (4c) relativistic CASSCF and 4c-CASPT2 in the spin-orbit-energy splitting calculations of the C, Si, and Ge atoms. Even for the fifth-row element Sn, the SOC-MRSF yielded accurate splittings (∼ 3 % error). In the SOC calculations of the molecular 4-thiothymine with a third-row element, SOC-MRSF values are in excellent agreement with those of the SO-GMC-QDPT2 level, regardless of geometries and exchange-correlation functionals. The same SOC-MRSF predicted the anticipated chance of S1 (nπ*) → T1 (ππ*) intersystem crossing, even in thymine with only second-row elements. With its accuracy and practicality, thus, SOC-MRSF is a promising electronic structure protocol in challenging situations such as nonadiabatic molecular dynamics (NAMD) incorporating both internal conversions and intersystem crossings in large systems.
Collapse
Affiliation(s)
- Konstantin Komarov
- Center for Quantum Dynamics, Pohang University of Science and Technology, Pohang37673, South Korea
| | - Woojin Park
- Department of Chemistry, Kyungpook National University, Daegu41566, South Korea
| | - Seunghoon Lee
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California91125, USA
| | - Tao Zeng
- Department of Chemistry, York University, Toronto, ONM3J 1P3, Canada
| | - Cheol Ho Choi
- Department of Chemistry, Kyungpook National University, Daegu41566, South Korea
| |
Collapse
|
5
|
Lunghi A, Sanvito S. Computational design of magnetic molecules and their environment using quantum chemistry, machine learning and multiscale simulations. Nat Rev Chem 2022; 6:761-781. [PMID: 37118096 DOI: 10.1038/s41570-022-00424-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/15/2022] [Indexed: 11/09/2022]
Abstract
Having served as a playground for fundamental studies on the physics of d and f electrons for almost a century, magnetic molecules are now becoming increasingly important for technological applications, such as magnetic resonance, data storage, spintronics and quantum information. All of these applications require the preservation and control of spins in time, an ability hampered by the interaction with the environment, namely with other spins, conduction electrons, molecular vibrations and electromagnetic fields. Thus, the design of a novel magnetic molecule with tailored properties is a formidable task, which does not only concern its electronic structures but also calls for a deep understanding of the interaction among all the degrees of freedom at play. This Review describes how state-of-the-art ab initio computational methods, combined with data-driven approaches to materials modelling, can be integrated into a fully multiscale strategy capable of defining design rules for magnetic molecules.
Collapse
|
6
|
Rooein M, Varganov SA. How to calculate the rate constants for nonradiative transitions between the MS components of spin multiplets? Mol Phys 2022. [DOI: 10.1080/00268976.2022.2116364] [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)
- Mitra Rooein
- Department of Chemistry, University of Nevada, Reno, NV, USA
| | | |
Collapse
|
7
|
Bian X, Wu Y, Rawlinson J, Littlejohn RG, Subotnik JE. Modeling Spin-Dependent Nonadiabatic Dynamics with Electronic Degeneracy: A Phase-Space Surface-Hopping Method. J Phys Chem Lett 2022; 13:7398-7404. [PMID: 35926097 DOI: 10.1021/acs.jpclett.2c01802] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Nuclear Berry curvature effects emerge from electronic spin degeneracy and can lead to nontrivial spin-dependent (nonadiabatic) nuclear dynamics. However, such effects are not captured fully by any current mixed quantum-classical method such as fewest-switches surface hopping. In this work, we present a phase-space surface-hopping (PSSH) approach to simulate singlet-triplet intersystem crossing dynamics. We show that with a simple pseudodiabatic ansatz, a PSSH algorithm can capture the relevant Berry curvature effects and make predictions in agreement with exact quantum dynamics for a simple singlet-triplet model Hamiltonian. Thus, this approach represents an important step toward simulating photochemical and spin processes concomitantly, as relevant to intersystem crossing and spin-lattice relaxation dynamics.
Collapse
Affiliation(s)
- Xuezhi Bian
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Yanze Wu
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Jonathan Rawlinson
- Department of Mathematics, University of Manchester, Manchester M13 9PL, U.K
| | - Robert G Littlejohn
- Department of Physics, University of California, Berkeley, California 94720, United States
| | - Joseph E Subotnik
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| |
Collapse
|
8
|
Wang Y, Guo H, Yarkony DR. Internal conversion and intersystem crossing dynamics based on coupled potential energy surfaces with full geometry-dependent spin-orbit and derivative couplings. Nonadiabatic photodissociation dynamics of NH 3(A) leading to the NH(X 3Σ -, a 1Δ) + H 2 channel. Phys Chem Chem Phys 2022; 24:15060-15067. [PMID: 35696936 DOI: 10.1039/d2cp01271e] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We simulate the photodissociation of NH3 originating from its first excited singlet state S1 into the NH2 + H (radical) and NH + H2 (molecular) channels. The states considered are the ground singlet state S0, the first excited singlet state S1 and the lowest-lying triplet state T1, which permit for the first time a uniform treatment of the internal conversion and intersystem crossing. The simulations are based on a diabatic potential energy matrix (DPEM) of S0, S1 coupled by a conical intersection seam, as well as a potential energy surface (PES) for T1 coupled by spin-orbit coupling (SOC) to the two singlet states. The DPEM and PES are fitted to ab initio electronic structure data (ESD) including energies, energy gradients, and derivative couplings. The DPEM also defines an adiabatic to diabatic state (AtD) transformation, which is used to transform the singular adiabatic SOC into a smooth function of the nuclear coordinates in the diabatic representation, allowing the diabatic SOC to be fit to an analytical functional form. ESD and SOC data obtained from these surfaces can serve as input for either quantum or semi-classical characterization of the nonadiabatic dynamics. Using the SHARC suite of programs, nonadiabatic simulations based on over 40 000 semi-classical trajectories assess the convergence of our results. The production of NH + H2 is not direct, but is only achieved through a quasi-statistical dissociation mechanism after internal conversion to the ground electronic state. This leads to a much lower yield comparing with the main NH2 + H channel. The NH(X3Σ_) radical produced through the intersystem crossing from S0 to T1 is rare (∼0.2%) compared to NH(a1Δ) due to the process being spin forbidden.
Collapse
Affiliation(s)
- Yuchen Wang
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA.
| | - Hua Guo
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, USA
| | - David R Yarkony
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA.
| |
Collapse
|
9
|
Lei Y, Zheng Z, Vasquez L, Zhao J, Ma J, Ma H. Enhanced Electron Transfer and Spin Flip through Spin-Orbital Couplings in Organic/Inorganic Heterojunctions: A Nonadiabatic Surface Hopping Simulation. J Phys Chem Lett 2022; 13:4840-4848. [PMID: 35616399 DOI: 10.1021/acs.jpclett.2c01177] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The circumstances of transferred electrons across organic/inorganic interfaces have attracted intensive interest because of the distinctive electronic structure properties of those two components. Leveraging ab initio nonadiabatic molecular dynamics methods in conjunction with spin dynamics induced by spin-orbital couplings (SOCs), this study reports two competitive channels during photoinduced dynamical processes in the prototypical ZnPc/monolayer MoS2 heterojunction. Interestingly, the electron-transfer and relaxation processes occur simultaneously because of the enhancement of electron-phonon couplings and expansion of dynamical pathways by SOCs, suggesting that the electron-transfer rate and relaxation processes can be tuned by SOCs, hence yielding the performance promotion of photovoltaic and photocatalytic devices. Additionally, approximately half of the transferred electrons flip their spin within 1.6 ps because of strong SOCs in MoS2, achieving great agreement with experimental measurements. This investigation provides instructive perspectives for designing novel devices and applications based on organic/inorganic heterojunctions, demonstrating the importance of spin dynamics simulations in exploring sophisticated photoinduced processes in materials.
Collapse
Affiliation(s)
- Yuli Lei
- Jiangsu Key Laboratory of Vehicle Emissions Control, Key Laboratory of Mesoscopic Chemistry of Ministry of Education, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Zhenfa Zheng
- Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Luis Vasquez
- Jiangsu Key Laboratory of Vehicle Emissions Control, Key Laboratory of Mesoscopic Chemistry of Ministry of Education, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Jin Zhao
- Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Jing Ma
- Jiangsu Key Laboratory of Vehicle Emissions Control, Key Laboratory of Mesoscopic Chemistry of Ministry of Education, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Haibo Ma
- Jiangsu Key Laboratory of Vehicle Emissions Control, Key Laboratory of Mesoscopic Chemistry of Ministry of Education, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| |
Collapse
|
10
|
Abstract
Intersystem crossing (ISC), a vital component of the electronic and nuclear transitions that compose photophysics, has been successfully simulated in light elements and transition metal complexes. Derived from the Z-dependent spin-orbit coupling (SOC), ISC is expected to be of greater importance in heavier elements, but few attempts have been made at the simulation of ISC in lanthanides or actinides. In this work, we explore several of the challenges that will need to be overcome in order to treat ISC in late-row elements, including the loss of spin as a good quantum number, the need to include SOC variationally via two- or four-component electronic structure, and the high density of states present in late-row complexes. Density functional theory (DFT) calculations are used to illustrate several of these effects, while a model Hamiltonian is used to illustrate the importance of momentum rescaling in surface hopping simulations of strongly coupled states.
Collapse
Affiliation(s)
- Andrew J S Valentine
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Xiaosong Li
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| |
Collapse
|
11
|
NAST: Nonadiabatic Statistical Theory Package for Predicting Kinetics of Spin-Dependent Processes. Top Curr Chem (Cham) 2022; 380:15. [PMID: 35201520 DOI: 10.1007/s41061-022-00366-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Accepted: 01/15/2022] [Indexed: 10/19/2022]
Abstract
We present a nonadiabatic statistical theory (NAST) package for predicting kinetics of spin-dependent processes, such as intersystem crossings, spin-forbidden unimolecular reactions, and spin crossovers. The NAST package can calculate the probabilities and rates of transitions between the electronic states of different spin multiplicities. Both the microcanonical (energy-dependent) and canonical (temperature-dependent) rate constants can be obtained. Quantum effects, including tunneling, zero-point vibrational energy, and reaction path interference, can be accounted for. In the limit of an adiabatic unimolecular reaction proceeding on a single electronic state, NAST reduces to the traditional transition state theory. Because NAST requires molecular properties at only a few points on potential energy surfaces, it can be applied to large molecular systems, used with accurate high-level electronic structure methods, and employed to study slow nonadiabatic processes. The essential NAST input data include the nuclear Hessian at the reactant minimum, as well as the nuclear Hessians, energy gradients, and spin-orbit coupling at the minimum energy crossing point (MECP) between two states. The additional computational tools included in the NAST package can be used to extract the required input data from the output files of electronic structure packages, calculate the effective Hessian at the MECP, and fit the reaction coordinate for more advanced NAST calculations. We describe the theory, its implementation, and three examples of application to different molecular systems.
Collapse
|
12
|
Heller ER, Richardson JO. Spin Crossover of Thiophosgene via Multidimensional Heavy-Atom Quantum Tunneling. J Am Chem Soc 2021; 143:20952-20961. [PMID: 34846871 DOI: 10.1021/jacs.1c10088] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The spin-crossover reaction of thiophosgene has drawn broad attention from both experimenters and theoreticians as a prime example of radiationless intramolecular decay via intersystem crossing. Despite multiple attempts over 20 years, theoretical predictions have typically been orders of magnitude in error relative to the experimentally measured triplet lifetime. We address the T1 → S0 transition by the first application of semiclassical golden-rule instanton theory in conjunction with on-the-fly electronic-structure calculations based on multireference perturbation theory. Our first-principles approach provides excellent agreement with the experimental rates. This was only possible because instanton theory goes beyond previous methods by locating the optimal tunneling pathway in full dimensionality and thus captures "corner cutting" effects. Since the reaction is situated in the Marcus inverted regime, the tunneling mechanism can be interpreted in terms of two classical trajectories, one traveling forward and one backward in imaginary time, which are connected by particle-antiparticle creation and annihilation events. The calculated mechanism indicates that the spin crossover is sped up by many orders of magnitude due to multidimensional quantum tunneling of the carbon atom even at room temperature.
Collapse
Affiliation(s)
- Eric R Heller
- Laboratory of Physical Chemistry, ETH Zürich, 8093 Zürich, Switzerland
| | | |
Collapse
|
13
|
Wang Y, Yarkony DR. Conical intersection seams in spin-orbit coupled systems with an even number of electrons: A numerical study based on neural network fit surfaces. J Chem Phys 2021; 155:174115. [PMID: 34742185 DOI: 10.1063/5.0067660] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In this work, we consider the existence and topography of seams of conical intersections (CIs) for two key singlet-triplet systems, including a uniformly scaled spin-orbit interaction. The basic one triplet and one singlet state system denoted as (S0,T1) and the two singlets and one triplet system denoted as (S0,S1,T1) are treated. Essential to this analysis are realistic electronic structure data taken from a recently reported neural network fit for the 1,21A and 13A states of NH3, including Hsf (spin-free) and Hso (spin-orbit) surfaces derived from high quality ab initio wavefunctions. Three types of seams for the (S0,S1,T1) system are reported, which depend on the choice of the electronic Hamiltonian, He. The nonrelativistic CI seam [He = Hsf, (S0,S1)], the energy minimized nonrelativistic singlet-triplet intersection seam [He = Hsf, (S0,T1)], and the fully relativistic seam in the spin-diabatic representation (He = Htot = Hsf + Hso) are reported as functions of R(N-H). The derivative couplings are computed using He = Htot and Hsf from the fit data. The line integral of the derivative coupling is employed to juxtapose the geometric phase in the relativistic, He = Htot, and nonrelativistic, He = Hsf, cases. It is found for the (S0,T1) system that there is no CI in the spin-adiabatic representation, while for the (S0,S1,T1) system, CI can only be formed for two pairs of spin-adiabatic electronic states. The geometric phase effect thus needs to be handled with care when it comes to spin-nonconserving dynamics simulations.
Collapse
Affiliation(s)
- Yuchen Wang
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - David R Yarkony
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA
| |
Collapse
|
14
|
Mukherjee S, Varganov SA. Intersystem crossing and internal conversion dynamics with GAIMS-TeraChem: Excited state relaxation in 2-cyclopentenone. J Chem Phys 2021; 155:174107. [PMID: 34742200 DOI: 10.1063/5.0068040] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Excited states relaxation in complex molecules often involves two types of nonradiative transitions, internal conversion (IC) and intersystem crossing (ISC). In the situations when the timescales of IC and ISC are comparable, an interplay between these two types of transitions can lead to complex nonadiabatic dynamics on multiple electronic states of different characters and spin multiplicities. We demonstrate that the generalized ab initio multiple spawning (GAIMS) method interfaced with the fast graphics processing unit-based TeraChem electronic structure code can be used to model such nonadiabatic dynamics involving both the IC and ISC transitions in molecules of moderate size. We carried out 1500 fs GAIMS simulations leading to the creation of up to 2500 trajectory basis functions to study the excited states relaxation in 2-cyclopentenone. After a vertical excitation from the ground state to the bright S2 state, the molecule quickly relaxes to the S1 state via conical intersection. The following relaxation proceeds along two competing pathways: one involves IC to the ground state, and the other is dominated by ISC to the low-lying triplet states. The time constants describing the population transfer between the six lowest singlet and triplet states predicted by the GAIMS dynamics are in good agreement with the characteristic times of IC and ISC obtained from the analysis of the time-resolved photoelectron spectrum.
Collapse
Affiliation(s)
- Saikat Mukherjee
- Department of Chemistry, University of Nevada, Reno, 1664 N. Virginia Street, Reno, Nevada 89557-0216, USA
| | - Sergey A Varganov
- Department of Chemistry, University of Nevada, Reno, 1664 N. Virginia Street, Reno, Nevada 89557-0216, USA
| |
Collapse
|