Empirical Valence-Bond Models for Reactive Potential Energy Surfaces Using Distributed Gaussians

and, H. Bernhard Schlegel; Sonnenberg, Jason L.

doi:10.1021/ct600084p

Cited by 59 publications

(118 citation statements)

References 28 publications

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“…The off-diagonal elements describe the coupling between the various states and are usually simple functions of the relevant internal coordinates. [12][13]22 A typical EVB eigenvalue equation assumes the form: …”

Section: Empirical Valence Bond Description Of the Reactionmentioning

confidence: 99%

Computational Study of Competition between Direct Abstraction and Addition–Elimination in the Reaction of Cl Atoms with Propene

et al. 2015

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Quasi-classical trajectory calculations on a newly constructed and full-dimensionality potential energy surface (PES) examine the dynamics of the reaction of Cl atoms with propene. The PES is an empirical valence bond (EVB) fit to high-level ab initio energies and incorporates deep potential energy wells for the 1-chloropropyl and 2-chloropropyl radicals, a direct H-atom abstraction route to HCl + allyl radical (CH2CHCH2·) products (∆ 298 = 63.1 kJ mol -1 ), and a pathway connecting these regions. In total, 94000 successful reactive trajectories were used to compute distributions of angular scattering and HCl vibrational and rotational level populations. These measures of the reaction dynamics agree satisfactorily with available experimental data. The dominant reaction pathway is direct abstraction of a hydrogen atom from the methyl group of propene occurring in under 500 fs. Fewer than 10% of trajectories follow an addition-elimination route via the two isomeric chloropropyl radicals. Large amplitude motions of the Cl about the propene molecular framework couple the addition intermediates to the direct abstraction pathway. The EVB method provides a good description of the complicated PES for the Cl + propene reaction despite fitting to a limited number of ab initio points, with the further advantage that dynamics specific to certain mechanisms can be studied in isolation by switching off coupling terms in the EVB matrix connecting different regions of the PES.

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Section: Empirical Valence Bond Description Of the Reactionmentioning

confidence: 99%

Computational Study of Competition between Direct Abstraction and Addition–Elimination in the Reaction of Cl Atoms with Propene

et al. 2015

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“…19,[39][40][41][42][43][44][45][46][47][48][49] Such approaches represent important molecular configurations using diabatic valence bond states, which are coupled using any of a wide range of schemes. 42,[50][51][52][53] So far, such approaches have largely been confined to simulation of reactions in enzymes, and for proton transfer in aqueous environments.…”

Section: Introductionmentioning

confidence: 99%

Non-equilibrium reaction and relaxation dynamics in a strongly interacting explicit solvent: F + CD3CN treated with a parallel multi-state EVB model

Glowacki

Orr-Ewing

Harvey

2015

The Journal of Chemical Physics

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We describe a parallelized linear-scaling computational framework developed to implement arbitrarily large multi-state empirical valence bond (MS-EVB) calculations within CHARMM and TINKER. Forces are obtained using the Hellmann-Feynman relationship, giving continuous gradients, and good energy conservation. Utilizing multi-dimensional Gaussian coupling elements fit to explicitly correlated coupled cluster theory, we built a 64-state MS-EVB model designed to study the F + CD3CN → DF + CD2CN reaction in CD3CN solvent (recently reported in Dunning et al. [Science 347(6221), 530 (2015)]). This approach allows us to build a reactive potential energy surface whose balanced accuracy and efficiency considerably surpass what we could achieve otherwise. We ran molecular dynamics simulations to examine a range of observables which follow in the wake of the reactive event: energy deposition in the nascent reaction products, vibrational relaxation rates of excited DF in CD3CN solvent, equilibrium power spectra of DF in CD3CN, and time dependent spectral shifts associated with relaxation of the nascent DF. Many of our results are in good agreement with time-resolved experimental observations, providing evidence for the accuracy of our MS-EVB framework in treating both the solute and solute/solvent interactions. The simulations provide additional insight into the dynamics at sub-picosecond time scales that are difficult to resolve experimentally. In particular, the simulations show that (immediately following deuterium abstraction) the nascent DF finds itself in a non-equilibrium regime in two different respects: (1) it is highly vibrationally excited, with ∼23 kcal mol−1 localized in the stretch and (2) its post-reaction solvation environment, in which it is not yet hydrogen-bonded to CD3CN solvent molecules, is intermediate between the non-interacting gas-phase limit and the solution-phase equilibrium limit. Vibrational relaxation of the nascent DF results in a spectral blue shift, while relaxation of the post-reaction solvation environment results in a red shift. These two competing effects mean that the post-reaction relaxation profile is distinct from what is observed when Franck-Condon vibrational excitation of DF occurs within a microsolvation environment initially at equilibrium. Our conclusions, along with the theoretical and parallel software framework presented in this paper, should be more broadly applicable to a range of complex reactive systems.

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“…1 (An alternative recently proposed is to fit V 12 by a polynomial times a spherical Gaussian. 26 ) Implementation of nuclear permutation symmetry into the MCMM algorithm will be described elsewhere.…”

Section: Introductionmentioning

confidence: 99%

Optimizing the Performance of the Multiconfiguration Molecular Mechanics Method

Tishchenko

Truhlar

2006

J. Phys. Chem. A

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Empirical Valence-Bond Models for Reactive Potential Energy Surfaces Using Distributed Gaussians

Cited by 59 publications

References 28 publications

Computational Study of Competition between Direct Abstraction and Addition–Elimination in the Reaction of Cl Atoms with Propene

Computational Study of Competition between Direct Abstraction and Addition–Elimination in the Reaction of Cl Atoms with Propene

Non-equilibrium reaction and relaxation dynamics in a strongly interacting explicit solvent: F + CD3CN treated with a parallel multi-state EVB model

Optimizing the Performance of the Multiconfiguration Molecular Mechanics Method

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