A comparison study of the H + CH₄ and H + SiH₄ reactions with eight-dimensional quantum dynamics: normal mode versus local mode in the reactant molecule vibration

Abstract

While molecular vibration of CH 4 is well described by the normal-mode paradigm, the local mode picture is more suitable for understanding the SiH 4 stretching vibrational motion. To compare the roles of the two types of molecular vibration in reaction dynamics, the H + CH₄ → H₂ + CH₃ and H + SiH₄ → H₂ + SiH₃ reactions have been investigated using an eight-dimensional (8D) quantum dynamics method in which the nonreacting XH₃ (X = C, Si) group keeps its C_3v symmetry in the reaction. The reaction probabilities, integral cross sections and thermal rate constants in the temperature range of 200 – 2,000 K were calculated for both reactions. Strong mode specifi city was found in both reactions, and the differences were rationalized by the vibrational characteristics of the CH₄ and SiH₄ reactants.

Dedicated to Professor Guosen Yan and published as part of the special collection of articles celebrating his 85th birthday.