An Improved Potential Energy Surface for the H₂Cl System and Its Use for Calculations of Rate Coefficients and Kinetic Isotope Effects

Abstract

We present a new potential energy surface (called G3) for the chemical reaction Cl + H2 → HCl + H. The new surface is based on a previous potential surface called GQQ, and it incorporates an improved bending potential that is fit to the results of ab initio electronic structure calculations. Calculations based on variational transition state theory with semiclassical transmission coefficients corresponding to an optimized multidimensional tunneling treatment (VTST/OMT, in particular improved canonical variational theory with least-action ground-state transmission coefficients) are carried out for nine different isotopomeric versions of the abstraction reaction and six different isotopomeric versions of the exchange reaction involving the H, D, and T isotopes of hydrogen, and the new surface is tested by comparing these calculations to available experimental data. The theoretical data are also used to investigate the equilibrium constant and the branching ratio for the reverse reaction, and calculations of these quantities are compared to the available experimental and theoretical data. Disciplines Chemistry CommentsReprinted (adapted) ReceiVed: March 13, 1996; In Final Form: May 15, 1996 X We present a new potential energy surface (called G3) for the chemical reaction Cl + H 2 f HCl + H. The new surface is based on a previous potential surface called GQQ, and it incorporates an improved bending potential that is fit to the results of ab initio electronic structure calculations. Calculations based on variational transition state theory with semiclassical transmission coefficients corresponding to an optimized multidimensional tunneling treatment (VTST/OMT, in particular improved canonical variational theory with leastaction ground-state transmission coefficients) are carried out for nine different isotopomeric versions of the abstraction reaction and six different isotopomeric versions of the exchange reaction involving the H, D, and T isotopes of hydrogen, and the new surface is tested by comparing these calculations to available experimental data. The theoretical data are also used to investigate the equilibrium constant and the branching ratio for the reverse reaction, and calculations of these quantities are compared to the available experimental and theoretical data.

High-temperature chemistry of HCl and Cl2

“…Theory [86,87] is in reasonable agreement with the experimental results. Figure 1 shows an Arrhenius plot for Cl + H 2 (R2).…”

Theoretical studies of product polarization and state distributions of the H+HCl reaction

“…As an important elementary step in the mechanism of the Cl 2 þ H 2 chain reaction which plays a major role in the development of chemical kinetics, the reaction of Cl þ H 2 and its isotopic variants have attracted enormous attention both experimentally and theoretically [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]. Decisive progress has been made towards precise knowledge of the above reactions by the constructing of a global potential energy surface (PES) called G3 [29], which has been used for a number of dynamical studies [28,[32][33][34][35][36][37][38][39][40].…”

“…Decisive progress has been made towards precise knowledge of the above reactions by the constructing of a global potential energy surface (PES) called G3 [29], which has been used for a number of dynamical studies [28,[32][33][34][35][36][37][38][39][40]. Comparison of the data between experiments and calculations on the G3 PES has shown the substantial adequacy of this PES to describe the ClHH reaction system.…”

Estudo teórico da estrutura eletrônica e da dinâmica induzida por lasers da molécula de HCl

“…Estudos teóricos, que se baseiam na construção de curvas de potencial, são uma consequência direta da aproximação de Born-Oppenheimer 1 e permitem a obtenção de diversas propriedades do sistema, como parâmetros espectroscópicos, caracterização de estados de transição, constantes de equilíbrio e superfícies de energia potencial (PES -Potential Energy Surface). 2,3 A obtenção de PES, que adequadamente descrevem um sistema molecular, constitui um dos fatores preponderantes nos estudos de dinâmica nuclear. É necessário conhecê-la para tratar a evolução temporal dos núcleos em diversos tipos de simulação computacional, tanto no emprego do formalismo clássico 4 quanto no do quântico.…”

“…Na literatura podem ser encontrados diversos estudos acerca da estrutura eletrônica do HCl, 2,3,8 incluindo a análise teórico-experimental do espectro Raman ressonante da camada L do átomo de cloro, 9 assim como do seu momento de dipolo. Por exemplo, na referência 10 a curva do momento de dipolo do HCl é obtida através de ajustes de dados de espectroscopia rovibracional, nas referências de Buldakov et al 11 e Maroulis 12 métodos semiempíricos e ab initio baseados nas teorias de perturbação de muitos corpos de 4ª Ordem e Coupled Cluster 1,13 são usados na obtenção da curva de energia potencial e do momento de dipolo em função da variação da distância entre os átomos de hidrogênio e cloro.…”