Journal ArticleDOI
Interpolated variational transition-state theory: Practical methods for estimating variational transition-state properties and tunneling contributions to chemical reaction rates from electronic structure calculations
Àngels González-Lafont,Àngels González-Lafont,Thanh N. Truong,Thanh N. Truong,Donald G. Truhlar +4 more
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TLDR
In this paper, the vibrational and entropic effects of variational transition state theory and the effective potentials and effective masses needed to calculate tunneling probabilities are estimated with a minimum of electronic structure information, thereby allowing their computation at a higher level of theory than would otherwise be possible.Abstract:
In many cases, variational transition states for a chemical reaction are significantly displaced from a saddle point because of zero‐point and entropic effects that depend on the reaction coordinate Such displacements are often controlled by the competition between the potential energy along the minimum‐energy reaction path and the energy requirements of one or more vibrational modes whose frequencies show a large variation along the reaction path In calculating reaction rates from potential‐energy functions we need to take account of these factors and—especially at lower temperatures—to include tunneling contributions, which also depend on the variation of vibrational frequencies along a reaction path To include these effects requires more information about the activated complex region of the potential‐energy surface than is required for conventional transition‐state theory In the present article we show how the vibrational and entropic effects of variational transition‐state theory and the effective potentials and effective masses needed to calculate tunneling probabilities can be estimated with a minimum of electronic structure information, thereby allowing their computation at a higher level of theory than would otherwise be possible As examples, we consider the reactions OH+H2, CH3+H2, and Cl+CH4 and some of their isotopic analogs We find for Cl+CH4→HCl+CH3 that the reaction rate is greatly enhanced by tunneling under conditions of interest for atmospheric chemistryread more
Citations
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TheRate: Program for Ab Initio Direct Dynamics Calculations of Thermal and Vibrational-State-Selected Rate Constants
TL;DR: The Rate Theoretical RATEs as mentioned in this paper is a complete application program with a graphical user interface GUI for calculating rate constants from first principles based on canonical variational transition-state theory.
Journal ArticleDOI
A Quantum Chemical and Classical Transition State Theory Explanation of Negative Activation Energies in OH Addition To Substituted Ethenes
TL;DR: In this paper, the authors used ab initio quantum chemical calculations and classical transition state theory to model the OH addition to ethene and obtained an overall rate constant of 11.7 × 10-12 cm3 molecule-1 s-1.
Journal ArticleDOI
Variational transition-state theory and semiclassical tunnelling calculations with interpolated corrections: a new approach to interfacing electronic structure theory and dynamics for organic reactions
TL;DR: In this article, a three-point or zero-order interpolated correction method is proposed to match the classical energies and vibration frequencies of some points (e.g. the reactant, saddle point, product, van der Waals complex, ion-molecule complex) along the minimum energy path (MEP) and in the reaction swath with high-level results.
Journal ArticleDOI
Thermal and vibrational‐state selected rates of the CH4+Cl↔HCl+CH3 reaction
TL;DR: In this article, a vibrational diabatic model was used for thermal and vibrational state selected rate calculations of CH4 +Cl↔CH3+HCl reaction and potential energy information was calculated by a combined density functional and molecular orbital approach.
Journal ArticleDOI
Potential energy surface, thermal, and state-selected rate coefficients, and kinetic isotope effects for Cl+CH4→HCl+CH3
TL;DR: In this article, a new potential energy surface for the gas-phase reaction Cl+CH4→HCl+CH3 was reported, which is based on the analytical function of Jordan and Gilbert for the analog reaction H+CH 4→H2+CH 3, and calibrated by using the experimental thermal rate coefficients and kinetic isotope effects.
References
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Journal ArticleDOI
Note on an Approximation Treatment for Many-Electron Systems
Chr. Møller,Milton S. Plesset +1 more
TL;DR: In this article, a perturbation theory for treating a system of n electrons in which the Hartree-Fock solution appears as the zero-order approximation was developed, and it was shown by this development that the first order correction for the energy and the charge density of the system is zero.
Chemical kinetics and photochemical data for use in stratospheric modeling
W. B. Demore,J. J. Margitan,Mario J. Molina,R. T. Watson,D. M. Golden,R. F. Hampson,Michael J. Kurylo,Carleton J. Howard,A. R. Ravishankara +8 more
TL;DR: As part of a series of evaluated sets, rate constants and photochemical cross sections compiled by the NASA Panel for Data Evaluation are provided in this article, with particular emphasis on the ozone layer and its possible perturbation by anthropogenic and natural phenomena.
Chemical kinetics and photochemical data for use in stratospheric modeling
W. B. Demore,Stanley P. Sander,D. M. Golden,R. F. Hampson,Michael J. Kurylo,Carleton J. Howard,A. R. Ravishankara,C. E. Kolb,Mario J. Molina +8 more
TL;DR: As part of a series of evaluated sets, rate constants and photochemical cross sections compiled by the NASA Panel for Data Evaluation are provided in this paper, with particular emphasis on the ozone layer and its possible perturbation by anthropogenic and natural phenomena.
Journal ArticleDOI
The Penetration of a Potential Barrier by Electrons
TL;DR: In this paper, the Schrodinger equation associated to the potential barrier is solved in terms of hypergeometric functions, and the coefficient of reflection for electrons approaching the barrier with energy $W$ is calculable.
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