Quantum dynamics study of the reaction H+SiH using a new potential energy surface of SiH₂（1¹A′）

Abstract

Initial state-selected and energy resolved reaction probabilities, integral cross sections（ICS） and the thermal rate constants of the H(²S)+<i>S</i>iH (X²П; <i>v</i>=0,<i>j</i>=0)→Si(¹D)+H₂(X¹Σ<_i>g</i>⁺) reaction are calculated within coupled states（CS） approximation and accurate calculation with full Coriolis coupling（CC） by a time-dependent wave packet propagation method (Chebyshev wave packet method). The new ab initio global potential energy surface (PES) of the electronic ground state (1¹A') of the system, recently reported by Li et al. [<i>Phys. Chem. Chem. Phys</i>., 2022, 24, 7759], is employed for the purpose. All partial wave contributions up to the total angular momentum <i>J</i>=80 for CS approximation and <i>J</i>=90 for CC calculation are considered to obtain the converged ICSs over a collision energy range of 1.0×10^-3-1.0 eV. The calculated probabilities and ICSs display a decreasing trend with the increase of the collision energy and show an oscillatory structure due to the SiH₂ well on the reaction path. The neglect of CC effect will lead to underestimation of the ICS and the rate constant due to the formation of a SiH₂ complex supported by the stationary points of the SiH₂（1¹A'）PES. In addition, the results of the exact calculation including CC effect are compared with those from the CS approximation. For the reaction probability, a similar trend of CC and CS calculations are observed at small total angular momentum <i>J</i>=10, 20 and 30, and the CC results are larger than the latter almost in the whole considered energy range at large total angular momentum <i>J</i>=40, 50, 60 and 70. The gap between CS and CC probabilities are increasing as <i>J</i> increases which reveals that Coriolis coupling effects get more and more important with increasing of <i>J</i> for the title reaction. Moreover, the exact quantum wave calculations show that the thermal rate constants between 300 K and 1000 K for the title reaction shows a temperature independent behavior similar to the H + CH reaction, but the value of the rate constant for the H + SiH reaction is an order of magnitude larger than that of the H + CH reaction.