Rate coefficients of a roaming reaction H + MgH using the ring polymer molecular dynamics

TL;DR

This paper applies ring-polymer molecular dynamics (RPMD) to calculate rate coefficients for a two-channel roaming reaction H + MgH, demonstrating RPMD's effectiveness for multi-channel reactions and comparing results with other theoretical methods.

Contribution

First application of RPMD to multi-channel roaming reactions, introducing new protocols for initial structure optimization and force constant selection.

Findings

RPMD results align with VTST and QD at certain conditions.

RPMD shows negative temperature dependence, consistent with VTST.

Results differ from ground state QD calculations.

Abstract

The ring-polymer molecular dynamics (RPMD) was used to calculate the thermal rate coefficients of the two-channel roaming reaction H + MgH. Both reaction channels, tight and roaming, are explicitly considered. This is a pioneering attempt of exerting RPMD method to multi-channel reactions. With the help of a newly developed optimization-interpolation protocol for preparing the initial structures and adaptive protocol for choosing the force constants, we have successfully obtained the thermal rate coefficients. The results are consistent with those from other theoretical methods, such as variational transition state theory (VTST) and quantum dynamics (QD). Especially, RPMD results exhibit negative temperature dependence, which is similar to results from VTST but different from ones from ground state QD calculations.