1
|
Tajouo Tela H, Quintas-Sánchez E, Dubernet ML, Scribano Y, Dawes R, Gatti F, Ndengué S. Rovibrational states calculations of the H 2O-HCN heterodimer with the multiconfiguration time dependent Hartree method. Phys Chem Chem Phys 2023; 25:31813-31824. [PMID: 37966067 DOI: 10.1039/d3cp03225f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2023]
Abstract
Water and hydrogen cyanide are two of the most common species in space and the atmosphere with the ability of binding to form dimers such as H2O-HCN. In the literature, while calculations characterizing various properties of the H2O-HCN cluster (equilibrium distance, vibrational frequencies and rotational constants) have been done in the past, extensive calculations of the rovibrational states of this system using a reliable quantum dynamical approach have yet to be reported. In this work, we intend to mend that by performing the first calculation of the rovibrational states of the H2O-HCN van der Waals complex on a recently developed potential energy surface. We use the block improved relaxation procedure implemented in the Heidelberg MultiConfiguration Time-Dependent Hartree (MCTDH) package to compute the states of the H2O-HCN isomer, from which we extract the transition frequencies and rotational constants of the complex. We further adapt an approach first suggested by Wang and Carrington-and supported here by analysis routines of the Heidelberg MCTDH package-to properly characterize the computed rovibrational states. The subsequent assignment of rovibrational states was done by theoretical analysis and visual inspection of the wavefunctions. Our simulations provide a Zero Point Energy (ZPE) and intermolecular vibrational frequencies in good agreement with past ab initio calculations. The transition frequencies and rotational constants obtained from our simulations match well with the available experimental data. This work has the broad aim to propose the MCTDH approach as a reliable option to compute and characterize rovibrational states of van der Waals complexes such as the current one.
Collapse
Affiliation(s)
- Hervé Tajouo Tela
- ICTP-East African Institute for Fundamental Research, University of Rwanda, Kigali, Rwanda.
| | - Ernesto Quintas-Sánchez
- Department of Chemistry, Missouri University of Science and Technology, 65409 Rolla, Missouri, USA
| | - Marie-Lise Dubernet
- LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne University, UPMC Univ Paris 06, 75014 Paris, France
| | - Yohann Scribano
- Laboratoire Univers et Particules de Montpellier, UMR-CNRS 5299, Université de Montpellier, Place Eugène Bataillon, 34095 Montpellier, France
| | - Richard Dawes
- Department of Chemistry, Missouri University of Science and Technology, 65409 Rolla, Missouri, USA
| | - Fabien Gatti
- Institut de Sciences Moleculaires d'Orsay, UMR 8214, Université Paris-Sud - Université Paris-Saclay, 91405 Orsay, France
| | - Steve Ndengué
- ICTP-East African Institute for Fundamental Research, University of Rwanda, Kigali, Rwanda.
- Department of Physics, Trinity College, 06106 Hartford, Connecticut, USA
| |
Collapse
|
2
|
A full-dimensional ab initio potential energy surface and rovibrational spectra for the Ar–SO2 complex. Theor Chem Acc 2022. [DOI: 10.1007/s00214-022-02914-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
3
|
Ammonia dimer: extremely fluxional but still hydrogen bonded. Nat Commun 2022; 13:1470. [PMID: 35304448 PMCID: PMC8933541 DOI: 10.1038/s41467-022-28862-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Accepted: 02/09/2022] [Indexed: 11/08/2022] Open
Abstract
In the 1980s, Nelson, Fraser, and Klemperer (NFK) published an experimentally derived structure of the ammonia dimer dramatically different from the structure determined computationally, which led these authors to the question "Does ammonia hydrogen bond?". This question has not yet been answered satisfactorily. To answer it, we have developed an ab initio potential energy surface (PES) for this dimer at the limits of the current computational capabilities and performed essentially exact six-dimensional calculations of the vibration-rotation-tunneling (VRT) spectra of NH3-NH3 and ND3-ND3, obtaining an unprecedented agreement with experimental spectra. In agreement with other recent electronic structure calculations, the global minimum on the PES is in a substantially bent hydrogen-bonded configuration. Since the bottom of the PES is exceptionally flat, the dimer is extremely fluxional and the probability of finding it in configurations that are not hydrogen bonded is high. Nevertheless, the probability of hydrogen-bonded configurations is large enough to consider the ammonia dimer to be hydrogen bonded. We also show that NFK's inference that the ammonia dimer is nearly rigid actually results from unusual cancellations between quantum effects that generate differences in spectra of different isotopologues.
Collapse
|
4
|
Serwatka T, Roy PN. Ground state of asymmetric tops with DMRG: Water in one dimension. J Chem Phys 2022; 156:044116. [DOI: 10.1063/5.0078770] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Tobias Serwatka
- Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Pierre-Nicholas Roy
- Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| |
Collapse
|
5
|
Martín Santa Daría A, Avila G, Mátyus E. Performance of a black-box-type rovibrational method in comparison with a tailor-made approach: Case study for the methane-water dimer. J Chem Phys 2021; 154:224302. [PMID: 34241197 DOI: 10.1063/5.0054512] [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
The present work intends to join and respond to the excellent and thoroughly documented rovibrational study of X. G. Wang and T. Carrington, Jr. [J. Chem. Phys. 154, 124112 (2021)] that used an approach tailored for floppy dimers with an analytic dimer Hamiltonian and a non-product basis set including Wigner D functions. It is shown in the present work that the GENIUSH black-box-type rovibrational method can approach the performance of the tailor-made computation for the example of the floppy methane-water dimer. Rovibrational transition energies and intensities are obtained in the black-box-type computation with a twice as large basis set and in excellent numerical agreement in comparison with the more efficient tailor-made approach.
Collapse
Affiliation(s)
| | - Gustavo Avila
- Institute of Chemistry, ELTE Eötvös Loránd University, Pázmány Péter sétány 1/A, 1117 Budapest, Hungary
| | - Edit Mátyus
- Institute of Chemistry, ELTE Eötvös Loránd University, Pázmány Péter sétány 1/A, 1117 Budapest, Hungary
| |
Collapse
|
6
|
Wang XG, Carrington T. Using nondirect product Wigner D basis functions and the symmetry-adapted Lanczos algorithm to compute the ro-vibrational spectrum of CH 4-H 2O. J Chem Phys 2021; 154:124112. [PMID: 33810654 DOI: 10.1063/5.0044010] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
By doing calculations on the methane-water van der Waals complex, we demonstrate that highly converged energy levels and wavefunctions can be obtained using Wigner D basis functions and the Symmetry-Adapted Lanczos (SAL) method. The Wigner D basis is a nondirect product basis and, therefore, efficient when the kinetic energy operator has accessible singularities. The SAL method makes it possible to exploit symmetry to label energy levels and reduce the cost of the calculation, without explicitly using symmetry-adapted basis functions. Line strengths are computed, and new bands are identified. In particular, we find unusually strong transitions between states associated with the isomers of the global minimum and the secondary minimum.
Collapse
Affiliation(s)
- Xiao-Gang Wang
- Chemistry Department, Queen's University, Kingston, Ontario K7L 3N6, Canada
| | - Tucker Carrington
- Chemistry Department, Queen's University, Kingston, Ontario K7L 3N6, Canada
| |
Collapse
|
7
|
A new six-dimensional ab initio potential energy surface and rovibrational spectra for the Ne–H2S complex. Chem Phys Lett 2021. [DOI: 10.1016/j.cplett.2020.138156] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
8
|
Han CY, Jiang T, Zhu H, Fan HJ. Six-dimensional ab initio potential energy surface and bound States for He-H 2S complex. CHINESE J CHEM PHYS 2020. [DOI: 10.1063/1674-0068/cjcp1907145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- Chao-ying Han
- School of Chemistry, Sichuan University, Chengdu 610064, China
| | - Ting Jiang
- School of Chemistry, Sichuan University, Chengdu 610064, China
| | - Hua Zhu
- School of Chemistry, Sichuan University, Chengdu 610064, China
| | - Hong-jun Fan
- School of Biological Engineering, Sichuan University of Science & Engineering, Zigong 643000, China
| |
Collapse
|
9
|
Jiang T, Han C, Zhu H. A new six-dimensional ab intito potential energy surface and rovibrational spectra for the Ar–H 2S complex. Mol Phys 2020. [DOI: 10.1080/00268976.2019.1612958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Ting Jiang
- School of Chemistry, Sichuan University, Chengdu, People’s Republic of China
| | - Chaoying Han
- School of Chemistry, Sichuan University, Chengdu, People’s Republic of China
| | - Hua Zhu
- School of Chemistry, Sichuan University, Chengdu, People’s Republic of China
| |
Collapse
|
10
|
Sur S, Ndengué SA, Quintas-Sánchez E, Bop C, Lique F, Dawes R. Rotationally inelastic scattering of O3–Ar: state-to-state rates with the multiconfigurational time dependent Hartree method. Phys Chem Chem Phys 2020; 22:1869-1880. [DOI: 10.1039/c9cp06501f] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The rates of state-changing collisions are compared for different isotopologues of ozone from quantum scattering calculations with the MCTDH method.
Collapse
Affiliation(s)
- Sangeeta Sur
- Department of Chemistry
- Missouri University of Science & Technology
- Rolla
- USA
| | - Steve A. Ndengué
- Department of Chemistry
- Missouri University of Science & Technology
- Rolla
- USA
- ICTP-East African Institute for Fundamental Research
| | | | - Cheikh Bop
- LOMC – UMR 6294
- CNRS-Université du Havre
- F-76063 Le Havre
- France
| | - François Lique
- LOMC – UMR 6294
- CNRS-Université du Havre
- F-76063 Le Havre
- France
| | - Richard Dawes
- Department of Chemistry
- Missouri University of Science & Technology
- Rolla
- USA
| |
Collapse
|
11
|
Ndengué S, Scribano Y, Gatti F, Dawes R. State-to-state inelastic rotational cross sections in five-atom systems with the multiconfiguration time dependent Hartree method. J Chem Phys 2019; 151:134301. [PMID: 31594314 DOI: 10.1063/1.5119381] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present a MultiConfiguration Time Dependent Hartree (MCTDH) method as an attractive alternative approach to the usual quantum close-coupling method that approaches some computational limits in the calculation of rotational excitation (and de-excitation) between polyatomic molecules (here collisions between triatomic and diatomic rigid molecules). We have performed a computational investigation of the rotational (de-)excitation of the benchmark rigid rotor H2O-H2 system on a recently developed Potential Energy Surface of the complex using the MCTDH method. We focus here on excitations and de-excitations from the 000, 111, and 110 states of H2O with H2 in its ground rotational state, looking at all the potential transitions in the energy range 1-200 cm-1. This work follows a recently completed study on the H2O-H2 cluster where we characterized its spectroscopy and more generally serves a broader goal to describe inelastic collision processes of high dimensional systems using the MCTDH method. We find that the cross sections obtained from the MCTDH calculations are in excellent agreement with time independent calculations from previous studies but does become challenging for the lower kinetic energy range of the de-excitation process: that is, below approximately 20 cm-1 of collision energy, calculations with a relative modest basis become unreliable. The MCTDH method therefore appears to be a useful complement to standard approaches to study inelastic collision for various collision partners, even at low energy, though performing better for rotational excitation than for de-excitation.
Collapse
Affiliation(s)
- Steve Ndengué
- ICTP-East African Institute for Fundamental Research, University of Rwanda, Kigali, Rwanda
| | - Yohann Scribano
- Laboratoire Univers et Particule de Montpellier, Université de Montpellier, UMR-CNRS 5299, 34095 Montpellier Cedex, France
| | - Fabien Gatti
- Institut de Sciences Moléculaires d'Orsay, UMR 8214, Université Paris-Sud - Université Paris-Saclay, 91405 Orsay, France
| | - Richard Dawes
- Department of Chemistry, Missouri University of Science and Technology, Rolla, Missouri 65409, USA
| |
Collapse
|
12
|
Zhang XL, Ma YT, Zhai Y, Li H. Full quantum calculation of the rovibrational states and intensities for a symmetric top-linear molecule dimer: Hamiltonian, basis set, and matrix elements. J Chem Phys 2019; 151:074301. [PMID: 31438702 DOI: 10.1063/1.5115496] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The rovibrational energy levels and intensities of the CH3F-H2 dimer have been obtained using our recent global intermolecular potential energy surface [X.-L. Zhang et al., J. Chem. Phys. 148, 124302 (2018)]. The Hamiltonian, basis set, and matrix elements are derived and given for a symmetric top-linear molecule complex. This approach to the generation of energy levels and wavefunctions can readily be utilized for studying the rovibrational spectra of other van der Waals complexes composed of a symmetric top molecule and a linear molecule, and may readily be extended to other complexes of nonlinear molecules and linear molecules. To confirm our method, the rovibrational levels of the H2O-H2 dimer have been computed and shown to be in good agreement with experiment and with previous theoretical results. The rovibrational Schrödinger equation has been solved using a Lanczos algorithm together with an uncoupled product basis set. As expected, dimers containing ortho-H2 are more strongly bound than dimers containing para-H2. Energies and wavefunctions of the discrete rovibrational levels of CH3F-paraH2 complexes obtained from the direct vibrationally averaged 5-dimensional potentials are in good agreement with the results of the reduced 3-dimensional adiabatic-hindered-rotor (AHR) approximation. Accurate calculations of the transition line strengths for the orthoCH3F-paraH2 complex are also carried out, and are consistent with results obtained using the AHR approximation. The microwave spectrum associated with the orthoCH3F-orthoH2 dimer has been predicted for the first time.
Collapse
Affiliation(s)
- Xiao-Long Zhang
- Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, 2519 Jiefang Road, Changchun 130023, China
| | - Yong-Tao Ma
- Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, 2519 Jiefang Road, Changchun 130023, China
| | - Yu Zhai
- Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, 2519 Jiefang Road, Changchun 130023, China
| | - Hui Li
- Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, 2519 Jiefang Road, Changchun 130023, China
| |
Collapse
|
13
|
Wang XG, Carrington T. Computing vibration-rotation-tunnelling levels of HOD dimer. Phys Chem Chem Phys 2019; 21:3527-3536. [PMID: 30123894 DOI: 10.1039/c8cp04451a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Using an accurate 6D water dimer potential energy surface, we compute vibration-rotation-tunnelling levels of HOD dimer, by assuming that the two monomers are rigid. HOD dimer has two isomers, a D-bonded isomer and an H-bonded isomer, and the wavefunctions of both isomers have amplitude in four wells. HOD dimer is important because, unlike the case of H2O dimer or D2O dimer, it is possible to measure the largest tunnelling splitting. Results for HOD dimer, therefore facilitate the testing of H2O dimer potentials. In J. Chem. Phys., 1995, 102, 1114, experimental results were interpreted in terms of 1D models. Experimental splittings of both isomers, obtained by fitting an energy level equation to spectra, are in good agreement with those we compute.
Collapse
Affiliation(s)
- Xiao-Gang Wang
- Chemistry Department, Queen's University, Kingston, Ontario K7L 3N6, Canada.
| | | |
Collapse
|
14
|
Sur S, Quintas-Sánchez E, Ndengué SA, Dawes R. Development of a potential energy surface for the O3–Ar system: rovibrational states of the complex. Phys Chem Chem Phys 2019; 21:9168-9180. [DOI: 10.1039/c9cp01044k] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Collisional stabilization is an important step in the process of atmospheric formation of ozone.
Collapse
Affiliation(s)
- Sangeeta Sur
- Department of Chemistry
- Missouri University of Science & Technology
- Rolla
- USA
| | | | - Steve A. Ndengué
- Department of Chemistry
- Missouri University of Science & Technology
- Rolla
- USA
| | - Richard Dawes
- Department of Chemistry
- Missouri University of Science & Technology
- Rolla
- USA
| |
Collapse
|
15
|
Intermolecular rovibrational bound states of H2O H2 dimer from a MultiConfiguration Time Dependent Hartree approach. Chem Phys Lett 2019. [DOI: 10.1016/j.cplett.2018.11.035] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
|
16
|
Vanfleteren T, Földes T, Herman M, Liévin J, Loreau J, Coudert LH. Experimental and theoretical investigations of H 2O-Ar. J Chem Phys 2018; 147:014302. [PMID: 28688396 DOI: 10.1063/1.4990738] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We have used continuous-wave cavity ring-down spectroscopy to record the spectrum of H2O-Ar in the 2OH excitation range of H2O. 24 sub-bands have been observed. Their rotational structure (Trot = 12 K) is analyzed and the lines are fitted separately for ortho and para species together with microwave and far infrared data from the literature, with a unitless standard deviation σ=0.98 and 1.31, respectively. Their vibrational analysis is supported by a theoretical input based on an intramolecular potential energy surface obtained through ab initio calculations and computation of the rotational energy of sub-states of the complex with the water monomer in excited vibrational states up to the first hexad. For the ground and (010) vibrational states, the theoretical results agree well with experimental energies and rotational constants in the literature. For the excited vibrational states of the first hexad, they guided the assignment of the observed sub-bands. The upper state vibrational predissociation lifetime is estimated to be 3 ns from observed spectral linewidths.
Collapse
Affiliation(s)
- Thomas Vanfleteren
- Service de Chimie Quantique et Photophysique, CP160/09, Faculté des Sciences, Université Libre de Bruxelles, 50, Ave., Roosevelt B-1050, Belgium
| | - Tomas Földes
- Service de Chimie Quantique et Photophysique, CP160/09, Faculté des Sciences, Université Libre de Bruxelles, 50, Ave., Roosevelt B-1050, Belgium
| | - Michel Herman
- Service de Chimie Quantique et Photophysique, CP160/09, Faculté des Sciences, Université Libre de Bruxelles, 50, Ave., Roosevelt B-1050, Belgium
| | - Jacques Liévin
- Service de Chimie Quantique et Photophysique, CP160/09, Faculté des Sciences, Université Libre de Bruxelles, 50, Ave., Roosevelt B-1050, Belgium
| | - Jérôme Loreau
- Service de Chimie Quantique et Photophysique, CP160/09, Faculté des Sciences, Université Libre de Bruxelles, 50, Ave., Roosevelt B-1050, Belgium
| | - Laurent H Coudert
- Institut des Sciences Moléculaires d'Orsay (ISMO), CNRS, Université Paris-Sud, Université Paris-Saclay, F-91405 Orsay, France
| |
Collapse
|
17
|
Wang XG, Carrington T. Using monomer vibrational wavefunctions to compute numerically exact (12D) rovibrational levels of water dimer. J Chem Phys 2018; 148:074108. [DOI: 10.1063/1.5020426] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Xiao-Gang Wang
- Chemistry Department, Queen’s University, Kingston, Ontario K7L 3N6, Canada
| | - Tucker Carrington
- Chemistry Department, Queen’s University, Kingston, Ontario K7L 3N6, Canada
| |
Collapse
|
18
|
Wang XG, Carrington T. Using monomer vibrational wavefunctions as contracted basis functions to compute rovibrational levels of an H2O-atom complex in full dimensionality. J Chem Phys 2017; 146:104105. [DOI: 10.1063/1.4977179] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Xiao-Gang Wang
- Chemistry Department, Queen’s University, Kingston, Ontario K7L 3N6, Canada
| | - Tucker Carrington
- Chemistry Department, Queen’s University, Kingston, Ontario K7L 3N6, Canada
| |
Collapse
|
19
|
Ndengué S, Dawes R, Gatti F, Meyer HD. Atom-triatom rigid rotor inelastic scattering with the MultiConfiguration Time Dependent Hartree approach. Chem Phys Lett 2017. [DOI: 10.1016/j.cplett.2016.12.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
|
20
|
Jones JR, Rouet FH, Lawler KV, Vecharynski E, Ibrahim KZ, Williams S, Abeln B, Yang C, McCurdy W, Haxton DJ, Li XS, Rescigno TN. An efficient basis set representation for calculating electrons in molecules. Mol Phys 2016. [DOI: 10.1080/00268976.2016.1176262] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Jeremiah R. Jones
- Chemical Sciences, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | | | - Keith V. Lawler
- Department of Chemistry, University of Nevada-Las Vegas, Las Vegas, NV, USA
| | - Eugene Vecharynski
- Computing Sciences, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Khaled Z. Ibrahim
- Computing Sciences, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Samuel Williams
- Computing Sciences, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Brant Abeln
- Department of Chemistry, University of California, Davis, Davis, CA, USA
- Ultrafast X-Ray Science Laboratory, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Chemical Sciences, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Chao Yang
- Computing Sciences, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - William McCurdy
- Department of Chemistry, University of California, Davis, Davis, CA, USA
- Ultrafast X-Ray Science Laboratory, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Chemical Sciences, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Daniel J. Haxton
- Ultrafast X-Ray Science Laboratory, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Chemical Sciences, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Xiaoye S. Li
- Computing Sciences, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Thomas N. Rescigno
- Chemical Sciences, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| |
Collapse
|
21
|
Yu HG. Multi-layer Lanczos iteration approach to calculations of vibrational energies and dipole transition intensities for polyatomic molecules. J Chem Phys 2015; 142:044106. [DOI: 10.1063/1.4906492] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Hua-Gen Yu
- Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973-5000, USA
| |
Collapse
|
22
|
Yu HG. Neural network iterative diagonalization method to solve eigenvalue problems in quantum mechanics. Phys Chem Chem Phys 2015; 17:14071-82. [DOI: 10.1039/c5cp01438g] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The neural network iterative diagonalization structure for computing the eigenstates of complex symmetric or Hermitian matrices.
Collapse
Affiliation(s)
- Hua-Gen Yu
- Department of Chemistry
- Brookhaven National Laboratory
- Upton
- USA
| |
Collapse
|
23
|
Felker PM. Fully quantal calculation of H2 translation-rotation states in the (p-H2)2@51264 clathrate hydrate inclusion compound. J Chem Phys 2014; 141:184305. [DOI: 10.1063/1.4901057] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
24
|
Brown J, Wang XG, Carrington T, Grubbs GS, Dawes R. Computational study of the rovibrational spectrum of CO2–CS2. J Chem Phys 2014; 140:114303. [DOI: 10.1063/1.4867792] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
25
|
Lei J, Zhou Y, Xie D. Theoretical Study on the Rotational Spectra of Ar‐D232S Complex. CHINESE J CHEM PHYS 2013. [DOI: 10.1063/1674-0068/26/06/656-660] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
|
26
|
Felker PM. Fully quantal calculation of H2 translation-rotation states in (H2)4@5(12)6(4) clathrate sII inclusion compounds. J Chem Phys 2013; 138:174306. [PMID: 23656133 DOI: 10.1063/1.4803117] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The quantal translation-rotation (TR) states of the (p-H2)4@5(12)6(4) and (o-D2)4@5(12)6(4) hydrate clathrate sII inclusion compounds have been computed by nuclear-orbital/configuration-interaction methods. The model of these compounds in a rigid, high-symmetry 5(12)6(4) cage is treated in detail. The low-energy TR level structures of both isotopomers within this model are found to consist of states that can be readily described in terms of a small number of single-H2 and double-H2 excitation modes. The use of the high-symmetry results to facilitate the calculation and interpretation of (p-H2)4 and (o-D2)4 TR states in low-symmetry physically realizable 5(12)6(4) cages is also reported.
Collapse
Affiliation(s)
- Peter M Felker
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, USA.
| |
Collapse
|
27
|
Sun X, Hu Y, Zhu H. Ab initio potential energy surface and predicted rotational spectra for the Ne–H2O complex. J Chem Phys 2013; 138:204312. [DOI: 10.1063/1.4807497] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
|
28
|
|
29
|
Felker PM. Nuclear-orbital/configuration-interaction study of coupled translation-rotation states in (H2)2@C70. J Chem Phys 2013; 138:044309. [PMID: 23387586 DOI: 10.1063/1.4776262] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The quantal translation-rotation states of two endohedral H(2) moieties in C(70) are computed by means of a nuclear-orbital/configuration-interaction method. H(2) "nuclear orbitals" are calculated as the translation-rotation eigenfunctions of one H(2) molecule interacting with C(70) and the mean field of the second H(2) molecule. Configurations are constructed as symmetrized bilinear products of these orbitals. These configurations are employed as the basis in which the matrix of the translation-rotation Hamiltonian of the cluster is computed and diagonalized. We show that this scheme allows for an efficient means to calculate the Hamiltonian matrix elements. We show that the configuration basis states represent excellent first approximations to the eigenstates of the species. Finally, we present results pertaining to the (H(2))(2)@C(70) low-energy translation-rotation level structure that can be understood in terms of a small number of H(2) excitation types.
Collapse
Affiliation(s)
- Peter M Felker
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, USA.
| |
Collapse
|
30
|
Lei J, Zhou Y, Xie D, Zhu H. A new ab initio intermolecular potential energy surface and predicted rotational spectra of the Kr−H2O complex. J Chem Phys 2012; 137:224314. [DOI: 10.1063/1.4770263] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
31
|
Szalay V, Ádám P. Variational properties of the discrete variable representation: discrete variable representation via effective operators. J Chem Phys 2012; 137:064118. [PMID: 22897266 DOI: 10.1063/1.4740486] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
A variational finite basis representation/discrete variable representation (FBR/DVR) Hamiltonian operator has been introduced. By calculating its matrix elements exactly one obtains, depending on the choice of the basis set, either a variational FBR or a variational DVR. The domain of grid points on which the FBR/DVR is variational has been shown to consist of the subsets of the set of grid points one obtains by diagonalizing commuting variational basis representations of the coordinate operators. The variational property implies that the optimal of the subsets of a fixed number of points, i.e., the subset which gives the possible highest accuracy eigenpairs, gives the DVR of the smallest trace. The symmetry properties of the variational FBR/DVR Hamiltonian operator are analyzed and methods to incorporate symmetry into FBR/DVR calculations are discussed. It is shown how the Fourier-basis FBR/DVR suitable to solving periodic systems arise within the theory presented. Numerical examples are given to illustrate the theoretical results. The use of variational effective Hamiltonian and coordinate operators has been instrumental in this study. They have been introduced in a novel way by exploiting quasi-Hermiticity.
Collapse
Affiliation(s)
- Viktor Szalay
- Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, P. O. Box 49, H-1525 Budapest, Hungary.
| | | |
Collapse
|
32
|
Lei J, Xiao M, Zhou Y, Xie D. A new ab initio intermolecular potential energy surface and predicted rotational spectra of the Ne-H2S complex. J Chem Phys 2012; 136:214307. [PMID: 22697543 DOI: 10.1063/1.4725715] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report a new three-dimensional ab initio intermolecular potential energy surface for the Ne-H(2)S complex with H(2)S monomer fixed at its experimental average structure. Using the supermolecular approach, the intermolecular potential energies were evaluated at CCSD(T) (coupled cluster with single and double and perturbative triple excitations) level with large basis sets including bond functions. The full counterpoise procedure was employed to correct the basis set superposition error. The planar T-shaped global minimum is located at the intermolecular distance of 3.51 Å with a well depth of 71.57 cm(-1). An additional planar local minimum was found to be separated from the global minimum with an energy barrier of 23.11 cm(-1). In addition, two first-order and one second-order saddle points were also located. The combined radial discrete variable representation/angular finite basis representation method and the Lanczos algorithm were employed to evaluate the rovibrational energy levels for eight isotopic species of the Ne-H(2)S complexes. The rotational transition frequencies for the eight isotopomers were also determined for the ground and first vibrational excited states, which are all in very good agreement with the available experimental values.
Collapse
Affiliation(s)
- Jinping Lei
- Institute of Theoretical and Computational Chemistry, Key Laboratory of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China
| | | | | | | |
Collapse
|
33
|
Scribano Y, Faure A, Lauvergnat D. Rotational excitation of H2O by para-H2 from an adiabatically reduced dimensional potential. J Chem Phys 2012; 136:094109. [DOI: 10.1063/1.3690881] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
|
34
|
Lei J, Zhou Y, Xie D. A new ab initio intermolecular potential energy surface and predicted rotational spectra of the Ar−H2S complex. J Chem Phys 2012; 136:084310. [DOI: 10.1063/1.3689443] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
35
|
Carrington T, Wang XG. Computing ro-vibrational spectra of van der Waals molecules. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2011. [DOI: 10.1002/wcms.73] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
36
|
Avila G, Carrington T. Using nonproduct quadrature grids to solve the vibrational Schrödinger equation in 12D. J Chem Phys 2011; 134:054126. [DOI: 10.1063/1.3549817] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
37
|
Schiffel G, Manthe U. On direct product based discrete variable representations for angular coordinates and the treatment of singular terms in the kinetic energy operator. Chem Phys 2010. [DOI: 10.1016/j.chemphys.2010.07.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
|
38
|
Avila G, Carrington T. Nonproduct quadrature grids for solving the vibrational Schrödinger equation. J Chem Phys 2009; 131:174103. [DOI: 10.1063/1.3246593] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
39
|
Leforestier C, van Harrevelt R, van der Avoird A. Vibration−Rotation−Tunneling Levels of the Water Dimer from an ab Initio Potential Surface with Flexible Monomers. J Phys Chem A 2009; 113:12285-94. [DOI: 10.1021/jp9020257] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Claude Leforestier
- Institut Charles Gerhardt Montpellier, UMR 5253-UM2-CNRS-ENSCM-UM1, CTMM, Bâtiment 15, CC 1501, Université Montpellier 2, 34095 Montpellier, Cedex 05, France
| | - Rob van Harrevelt
- Theoretical Chemistry, Institute for Molecules and Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Ad van der Avoird
- Theoretical Chemistry, Institute for Molecules and Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| |
Collapse
|
40
|
Olsen RA, McCormack DA, Luppi M, Baerends EJ. Six-dimensional quantum dynamics of H2 dissociative adsorption on the Pt(211) stepped surface. J Chem Phys 2008; 128:194715. [DOI: 10.1063/1.2920488] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
|
41
|
Wang XG, Carrington T. Using a nondirect product discrete variable representation for angular coordinates to compute vibrational levels of polyatomic molecules. J Chem Phys 2008; 128:194109. [DOI: 10.1063/1.2918498] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
42
|
Cencek W, Szalewicz K, Leforestier C, van Harrevelt R, van der Avoird A. An accurate analytic representation of the water pair potential. Phys Chem Chem Phys 2008; 10:4716-31. [DOI: 10.1039/b809435g] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
|
43
|
Manzhos S, Carrington T. Using redundant coordinates to represent potential energy surfaces with lower-dimensional functions. J Chem Phys 2007; 127:014103. [PMID: 17627333 DOI: 10.1063/1.2746846] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We propose a method for fitting potential energy surfaces with a sum of component functions of lower dimensionality. This form facilitates quantum dynamics calculations. We show that it is possible to reduce the dimensionality of the component functions by introducing new and redundant coordinates obtained with linear transformations. The transformations are obtained from a neural network. Different coordinates are used for different component functions and the new coordinates are determined as the potential is fitted. The quality of the fits and the generality of the method are illustrated by fitting reference potential surfaces of hydrogen peroxide and of the reaction OH+H(2)-->H(2)O+H.
Collapse
Affiliation(s)
- Sergei Manzhos
- Département de Chimie, Université de Montréal, CP 6128, succursale Centre-ville, Montréal (Québec) H3C 3J7, Canada.
| | | |
Collapse
|
44
|
Recursive Solutions to Large Eigenproblems in Molecular Spectroscopy and Reaction Dynamics. REVIEWS IN COMPUTATIONAL CHEMISTRY 2007. [DOI: 10.1002/9780470189078.ch7] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
|
45
|
Light JC, Carrington T. Discrete-Variable Representations and their Utilization. ADVANCES IN CHEMICAL PHYSICS 2007. [DOI: 10.1002/9780470141731.ch4] [Citation(s) in RCA: 419] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
|
46
|
Szalay V. Optimal grids for generalized finite basis and discrete variable representations: definition and method of calculation. J Chem Phys 2006; 125:154115. [PMID: 17059247 DOI: 10.1063/1.2358979] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The method of optimal generalized finite basis and discrete variable representations (FBR and DVR) generalizes the standard, Gaussian quadrature grid-classical orthonormal polynomial basis-based FBR/DVR method to general sets of grid points and to general, nondirect product, and/or nonpolynomial bases. Here, it is shown how an optimal set of grid points can be obtained for an optimal generalized FBR/DVR calculation with a given truncated basis. Basis set optimized and potential optimized grids are defined. The optimized grids are shown to minimize a function of grid points derived by relating the optimal generalized FBR of a Hamiltonian operator to a non-Hermitian effective Hamiltonian matrix. Locating the global minimum of this function can be reduced to finding the zeros of a function in the case of one dimensional problems and to solving a system of D nonlinear equations repeatedly in the case of D>1 dimensional problems when there is an equal number of grid points and basis functions. Gaussian quadrature grids are shown to be basis optimized grids. It is demonstrated by a numerical example that an optimal generalized FBR/DVR calculation of the eigenvalues of a Hamiltonian operator with potential optimized grids can have orders of magnitude higher accuracy than a variational calculation employing the same truncated basis. Nevertheless, for numerical integration with the optimal generalized FBR quadrature rule basis optimized grids are the best among grids of the same number of points. The notions of Gaussian quadrature and Gaussian quadrature accuracy are extended to general, multivariable basis functions.
Collapse
Affiliation(s)
- Viktor Szalay
- Crystal Physics Laboratory, Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary.
| |
Collapse
|
47
|
Manzhos S, Carrington T. A random-sampling high dimensional model representation neural network for building potential energy surfaces. J Chem Phys 2006; 125:084109. [PMID: 16965003 DOI: 10.1063/1.2336223] [Citation(s) in RCA: 155] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We combine the high dimensional model representation (HDMR) idea of Rabitz and co-workers [J. Phys. Chem. 110, 2474 (2006)] with neural network (NN) fits to obtain an effective means of building multidimensional potentials. We verify that it is possible to determine an accurate many-dimensional potential by doing low dimensional fits. The final potential is a sum of terms each of which depends on a subset of the coordinates. This form facilitates quantum dynamics calculations. We use NNs to represent HDMR component functions that minimize error mode term by mode term. This NN procedure makes it possible to construct high-order component functions which in turn enable us to determine a good potential. It is shown that the number of available potential points determines the order of the HDMR which should be used.
Collapse
Affiliation(s)
- Sergei Manzhos
- Département de chimie, Université de Montréal, Case postale 6128, succursale Centre-ville, Montréal (Québec) H3C 3J7, Canada.
| | | |
Collapse
|
48
|
Czakó G, Szalay V, Császár AG. Finite basis representations with nondirect product basis functions having structure similar to that of spherical harmonics. J Chem Phys 2006; 124:14110. [PMID: 16409027 DOI: 10.1063/1.2141947] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The currently most efficient finite basis representation (FBR) method [Corey et al., in Numerical Grid Methods and Their Applications to Schrodinger Equation, NATO ASI Series C, edited by C. Cerjan (Kluwer Academic, New York, 1993), Vol. 412, p. 1; Bramley et al., J. Chem. Phys. 100, 6175 (1994)] designed specifically to deal with nondirect product bases of structures phi(n) (l)(s)f(l)(u), chi(m) (l)(t)phi(n) (l)(s)f(l)(u), etc., employs very special l-independent grids and results in a symmetric FBR. While highly efficient, this method is not general enough. For instance, it cannot deal with nondirect product bases of the above structure efficiently if the functions phi(n) (l)(s) [and/or chi(m) (l)(t)] are discrete variable representation (DVR) functions of the infinite type. The optimal-generalized FBR(DVR) method [V. Szalay, J. Chem. Phys. 105, 6940 (1996)] is designed to deal with general, i.e., direct and/or nondirect product, bases and grids. This robust method, however, is too general, and its direct application can result in inefficient computer codes [Czako et al., J. Chem. Phys. 122, 024101 (2005)]. It is shown here how the optimal-generalized FBR method can be simplified in the case of nondirect product bases of structures phi(n) (l)(s)f(l)(u), chi(m) (l)(t)phi(n) (l)(s)f(l)(u), etc. As a result the commonly used symmetric FBR is recovered and simplified nonsymmetric FBRs utilizing very special l-dependent grids are obtained. The nonsymmetric FBRs are more general than the symmetric FBR in that they can be employed efficiently even when the functions phi(n) (l)(s) [and/or chi(m) (l)(t)] are DVR functions of the infinite type. Arithmetic operation counts and a simple numerical example presented show unambiguously that setting up the Hamiltonian matrix requires significantly less computer time when using one of the proposed nonsymmetric FBRs than that in the symmetric FBR. Therefore, application of this nonsymmetric FBR is more efficient than that of the symmetric FBR when one wants to diagonalize the Hamiltonian matrix either by a direct or via a basis-set contraction method. Enormous decrease of computer time can be achieved, with respect to a direct application of the optimal-generalized FBR, by employing one of the simplified nonsymmetric FBRs as is demonstrated in noniterative calculations of the low-lying vibrational energy levels of the H3+ molecular ion. The arithmetic operation counts of the Hamiltonian matrix vector products and the properties of a recently developed diagonalization method [Andreozzi et al., J. Phys. A Math. Gen. 35, L61 (2002)] suggest that the nonsymmetric FBR applied along with this particular diagonalization method is suitable to large scale iterative calculations. Whether or not the nonsymmetric FBR is competitive with the symmetric FBR in large-scale iterative calculations still has to be investigated numerically.
Collapse
Affiliation(s)
- Gábor Czakó
- Institute of Chemistry, Eötvös University, P.O. Box 32, H-1518 Budapest 112, Hungary
| | | | | |
Collapse
|
49
|
|
50
|
Wang XG, Carrington T. Improving the calculation of rovibrational spectra of five-atom molecules with three identical atoms by using a C3υ(G6) symmetry-adapted grid: Applied to CH3D and CHD3. J Chem Phys 2005; 123:154303. [PMID: 16252944 DOI: 10.1063/1.2043148] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In this paper we report two improvements on the approach we have used to compute rovibrational levels of methane and apply the new ideas to calculate rovibrational levels of two methane isotopomers CH3D and CHD3. Both improvements make the bend calculation better. The first improvement is a G6-invariant (or C3upsilon-invariant) grid which is designed such that each point on the grid is mapped to another point on the grid by any of the G6 operations. The second improvement is the use of fast Fourier transform (FFT) to compute the bend potential matrix-vector products. The FFT matrix-vector product is about three and ten times faster than the previous sequential summation method for the J=0 and J>0 cases, respectively. The calculated J=1 rovibrational levels of CH3D and CHD3 on the Schwenke and Partridge [Spectrochim. Acta, Part A 57, 887 (2001)] ab initio potential are in good agreement (within 6 cm(-1) for the levels up to 3000 cm(-1)) with the experimental data. The agreement is even better (within 0.1 cm(-1) for the levels up to 6000 cm(-1)) if the associated J=0 energies are subtracted.
Collapse
Affiliation(s)
- Xiao-Gang Wang
- Départment de chimie, Université de Montréal, CP 6128, succursale Centre-ville, Montréal (Québec) H3C 3J7, Canada.
| | | |
Collapse
|