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

Variational Transition State Theory (VTST) calculations of the thermal rate coefficients of the reaction of O(P-3) with HCl are presented. Four potent ial surfaces for the 3A " State are studied, three of them due to Ramachand ran, Senekonitsch and Wyatt (RSW), based on fits to scaled MR-CISD + Q ener gies, and the fourth due to Koizumi, Schatz and Gordon (KSG), based on scal ed MP2/6-31G(d,p) energies. Using the program POLYRATE, version 7.3, the ra te coefficients are calculated using Improved Canonical Variational Theory (ICVT) with the microcanonical Optimized Multidimensional Tunneling (mu OMT ) approximation over the temperature range 200-1500K. These results are com pared 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 go od agreement for T > 500K, while those computed on the KSG surface are some what higher. These comparisons indicate that one of the RSW surfaces may es tablish an upper limit for the correct reaction barrier for this reaction, while the KSG surface could provide a lower limit. (C) 1998 Elsevier Scienc e B.V. All rights reserved.