Ab Initio Potential Energy Surface for the H + OCS Reaction
Final rept. Feb 1992-Feb 1993
ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
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An ab initio MP4 study has been made of the potential energy surface of the H OCS reaction. 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 the, with energy refinements at the MP4SDTQ level. Six minima corresponding to confomers of the HOCS system were calculated and transition states leading into and out of these minima were determined. 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 earlier experimental hypotheses of the existence of stable, four-body reaction intermediates, as well as tight four-body transition states leading to products. Our results also show that these transition states have nonlinear structures, contrary to assumptions made in earlier experimental work. Our calculations provide the first set of structural data that detail the reaction mechanisms for H OCS going to SH CO or OH CS. In addition, the feature of this potential energy surface suggest explanations for observed nonstatistical behavior in product energy distributions of the SH CO channel, and the statistical behavior observed in the product energy distributions of the OH CS channel. Potential energy surface, Ab initio, MP4, Electronic structure, Potential energy, Quantum chemistry.
- Physical Chemistry