Vibrational Coupled Cluster Computations in Polyspherical Coordinates with the Exact Analytical Kinetic Energy Operator

Klinting, Emil Lund; Lauvergnat, David; Christiansen, Ove

doi:10.1021/acs.jctc.0c00261

“…This limits the types of nuclear motion that can be well-represented by these calculations, and is e.g. the impetus behind recent work by Klinting et al 47 and by Carrington et al. 48 Other full SE solution software, e.g.…”

Section: Methodsmentioning

confidence: 99%

Coupled Anharmonic Thermochemistry from Stratified Monte-Carlo Integration

Rath¹,

Kopp²,

Leonhard³

2021

Preprint

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This study presents CIMCI, a new semi-classical method for handling fully coupled anharmonicity in gas-phase thermodynamics that promises to be black-boxable, to be applicable for all kinds of anharmonicity, and to scale better at higher dimensionality than other methods for handling gas-phase molecular anharmonicity. The method does so by using automatically and recursively stratified, simultaneous Monte Carlo integration of multiple functions. For the small systems analyzed by this study, the method’s anharmonic corrections match reference data better than those of other blackbox anharmonic methods, e.g. VPT2. This holds even when sampling with CIMCI is done with primitive force fields, e.g. UFF, while the competing methods are used with proper, comprehensive potentials, e.g. the M06-2X meta-hybrid DFT functional. With further refinements in Monte Carlo sampling efficiency, in the quality of fast potentials practical for Monte Carlo sampling, and in automatic detection of which stereoisomers should be included during sampling, CIMCI has the potential to be the ideal anharmonic treatment for larger molecules where the large number of conformers and the high dimensionality of coupled torsions present major difficulties for other, existing treatments for anharmonicity.

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“…This feature is numerically very interesting in quantum dynamics because the KEO action on a wave function or a wavepacket does not require a multi-dimensional grid explicitly. Therefore, these coordinates are heavily used in many applications or approaches such as the multi-configurational time-dependent Hartree method (MCTDH) [7,13,38] and the vibrational configuration interaction or vibrational coupled cluster methods [39]. Furthermore, some of the authors were able to develop a numerical code, T ana [14,15,40], to get analytical expressions for molecular systems of any size with a lot of freedom in the selection of the vector parametrization and the subsystems (local BF frames).…”

Section: Coordinates and Kinetic Energy Operatormentioning

confidence: 99%

Quantum dynamics with curvilinear coordinates: models and kinetic energy operator

Marsili

¹

,

Agostini

²

,

Nauts

³

et al. 2022

Phil. Trans. R. Soc. A.

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In order to simplify the numerical solution of the time-dependent or time-independent Schrödinger equations associated with atomic and molecular motions, the use of well-adapted coordinates is essential. Usually, this set of curvilinear coordinates leads to a Hamiltonian operator that is as separable as possible. Although their corresponding kinetic energy operator (KEO) expressions can be derived analytically for small systems or special kinds of coordinates, a numerical and exact approach allows one to compute them in terms of sophisticated curvilinear coordinates. Furthermore, the numerical approach enables one to easily define reduced-dimensionality or constrained models. We present here a recent implementation of this numerical approach that allows nested coordinate transformations, therefore leading to great flexibility in the definition of the curvilinear coordinates. Furthermore, this implementation has no limitations in terms of numbers of atoms or coordinate transformations. The quantum dynamics of the cis–trans photoisomerization of part of the retinal chromophore illustrates the construction of the coordinates and KEO part of a three-dimensional model. This article is part of the theme issue ‘Chemistry without the Born–Oppenheimer approximation’.

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“…This limits the types of nuclear motion that can be well-represented by these calculations, and is e.g. the impetus behind recent work by Klinting et al 47 and by cally evaluate kinetic energy operators and compute energy levels with Lanczos solvers. More recently, analytical expressions of kinetic energy operators for these methods were shown to also be possible.…”

Section: State-of-the-artmentioning

confidence: 99%

Coupled Anharmonic Thermochemistry from Stratified Monte-Carlo Integration

Rath¹,

Kopp

²

,

Leonhard³

2021

Preprint

1

0

View full text Add to dashboard Cite

This study presents CIMCI, a new semi-classical method for handling fully coupled anharmonicity in gas-phase thermodynamics that promises to be black-boxable, to be applicable for all kinds of anharmonicity, and to scale better at higher dimensionality than other methods for handling gas-phase molecular anharmonicity. The method does so by using automatically and recursively stratified, simultaneous Monte Carlo integration of multiple functions. For the small systems analyzed by this study, the method’s anharmonic corrections match reference data better than those of other blackbox anharmonic methods, e.g. VPT2. This holds even when sampling with CIMCI is done with primitive force fields, e.g. UFF, while the competing methods are used with proper, comprehensive potentials, e.g. the M06-2X meta-hybrid DFT functional. With further refinements in Monte Carlo sampling efficiency, in the quality of fast potentials practical for Monte Carlo sampling, and in automatic detection of which stereoisomers should be included during sampling, CIMCI has the potential to be the ideal anharmonic treatment for larger molecules where the large number of conformers and the high dimensionality of coupled torsions present major difficulties for other, existing treatments for anharmonicity.

show abstract

Vibrational Coupled Cluster Computations in Polyspherical Coordinates with the Exact Analytical Kinetic Energy Operator

Cited by 15 publications

References 153 publications

Coupled Anharmonic Thermochemistry from Stratified Monte-Carlo Integration

Coupled Anharmonic Thermochemistry from Stratified Monte-Carlo Integration

Quantum dynamics with curvilinear coordinates: models and kinetic energy operator

Coupled Anharmonic Thermochemistry from Stratified Monte-Carlo Integration

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