  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.
