Variational transition state theory calculations of thermal rate coefficients for the O( 3P)+HCl reaction

Abstract

Variational Transition State Theory (VTST) calculations of the thermal rate coefficients of the reaction of O( 3 P) with HCl are presented. Four potential surfaces for the 3 A″ state are studied, three of them due to Ramachandran, Senekowitsch and Wyatt (RSW), based on fits to scaled MR-CISD+Q energies, and the fourth due to Koizumi, Schatz and Gordon (KSG), based on scaled MP2/6-31G( d, p) energies. Using the program POLYRATE, version 7.3, the rate coefficients are calculated using Improved Canonical Variational Theory (ICVT) with the microcanonical Optimized Multidimensional Tunneling (μOMT) approximation over the temperature range 200–1500K. These results are compared to available experimental data, which lie in the range 293–1486K. It is found that the RSW surfaces yield thermal rate coefficients that are in reasonable agreement with experimental data over this range, and in very good agreement for T>500K, while those computed on the KSG surface are somewhat higher. These comparisons indicate that one of the RSW surfaces may establish an upper limit for the correct reaction barrier for this reaction, while the KSG surface could provide a lower limit.