A new class of reaction path based potential energy surfaces enabling accurate black box chemical rate constant calculations

Abstract

A new method for constructing a full-dimensional potential energy surface representation in black-box fashion for an arbitrary reaction is presented. With limited knowledge of the system and with a limited number of reference-level data points, it is possible to calculate reaction rate constants with high quality. Building on our recently published application of Grimme’s quantum-mechanically derived force field (QMDFF) and its empirical valence bond extension EVB-QMDFF to rate constant calculations, an improved EVB coupling method with local corrections was developed in order to avoid spurious problems for certain systems and hence to achieve an even wider range of applicability. A given reaction path (RP) is modeled as a parametric curve via cubic spline interpolation; regions offside this path are then extrapolated with quadratic Taylor series, and regions around the transition state are corrected by introduction of direct reference interpolation; the method is named transition region corrected RP-EVB-QMDFF (TREQ). To verify the quality of TREQ, six reactions were chosen for which full-dimensional analytical potential surfaces are available in the literature. Chemical reaction rates were calculated with ring polymer molecular dynamics on the reference surfaces as well as on the TREQ surfaces resulting in excellent agreement.

Reactive Molecular Dynamics at Constant Pressure via Nonreactive Force Fields: Extending the Empirical Valence Bond Method to the Isothermal-Isobaric Ensemble

“…In contrast, if the choice was to use coupling terms that do not depend on mk but other degrees of freedom such as spatial coordinates (see refs. [40][41][42][43][44][45][46], we cannot discern a clear logic to derive an expression for σ EVB , which might explain the fact there is no evidence of any previous reported method to compute the stress tensor using EVB.…”

“…Several sophisticated EVB coupling recipes have been proposed over the years. 23,[40][41][42][43][44][45][46]51,52 Despite their proven success, these recipes use complex internal (spatial) coordinates to couple the force fields. Here, however, we aim to use functional forms C mk that depend on the energy…”

Reactive molecular dynamics at constant pressure via non-reactive force fields: extending the Empirical Valence Bond method to the isothermal-isobaric ensemble

“…In contrast, if the choice was to use coupling terms that do not depend on ǫ mk but other degrees of freedom such as spatial coordinates (see refs. [38][39][40][41][42][43][44], we cannot discern a clear logic to derive an expression for σ EVB , which might explain the fact there is no evidence of any previous reported method to compute the stress tensor using EVB.…”

“…Several sophisticated EVB coupling recipes have been proposed over the years. [38][39][40][41][42][43][44] Despite their proven success, these recipes use complex internal (spatial) coordinates to couple the force fields. Here, however, we aim to use functional forms C mk that depend on the energy gaps…”

Theoretical evaluation of equilibrium constant for boron isotopes exchange between boric acid and borate in pure and saline water

“…Nevertheless, NMA with the explicit solvent approach cannot be conveniently employed for studying multicomponent solvents since achieving appropriate sampling of a canonical ensemble in this way is challenging. Consequently, theoretical evaluation of k 3−4 in saline water is achieved via NMA with the implicit solvent approach [21] as well as path integral molecular dynamics [22,23]. The latter method also allows studying the anharmonicity impacts on the calculated partition functions.…”