AB-INITIO POTENTIAL-ENERGY SURFACE FOR THE H+OCS REACTION

An ab initio MP4 study has been made of the potential energy surface of the H + OCS reaction. Minima and saddle points leading to formation of OH + CS or SH + CO were found. Stationary points were located using the 6-31G** basis set at the ROHF and UMP2 levels of theory, with energy refinements at the MP4(SDTQ) level. This theoretical study, in conjunction with the recent experimental results of Bohmer, Mikhaylichenko and Wittig, provides a mechanistic overview of the reactions of the H + OCS system. The results substantiate experimental hypotheses of the existence of stable, four-body reaction intermediates, as well as ''tight'' four-body transition states leading to products. Our calculations provide the first set of structural data that detail the reaction mechanisms for H + OCS going to SH + CO or OH + CS.