Theoretical study of the non-Arrhenius temperature dependence of thermal rate constants for the H+H2S -> H-2+SH reaction

Thermal rate constants for the H + H2S --> H-2 + SH reaction have been calc ulated over a temperature range of 100-2500 K using variational transition state theory combined with the multidimensional semiclassical tunneling cor rection. Potential energy curves for the reaction have been calculated usin g the spin-projected fourth-order Moller-Plesset perturbation method and qu adratic configuration-interaction method with the correlation-consistent po larized valence triple-zeta basis set. The calculated rate constants agree quite well with experiment over a wide range of temperature; in particular, excellent agreement with experiment is obtained around room temperatures. We have thus succeeded in quantitatively predicting the non-Arrhenius tempe rature dependence of thermal rate constants for the present reaction withou t adjusting any potential parameters, which has been observed recently by Y oshimura [Chem. Phys. Lett. 189, 199 (1992)] and by Peng, Hu, and Marshall [J. Phys. Chem. 103, 5307 (1999)]. (C) 1999 American Institute of Physics. [S0021-9606(99)01547-0].