Communication: nonadiabatic ring-polymer molecular dynamics.

A new method based on an extension of ring-polymer molecular dynamics is proposed for the calculation of thermal correlation functions in electronically nonadiabatic systems. The ring-polymer dynamics are performed using a continuous-variable representation of the electronic states within the mapping approach, such that the electronic and nuclear degrees of freedom are treated on an equal footing. Illustrative applications of the method show good agreement with exact quantum results for the dynamics over short to moderate times and reveal a systematic improvement over the classical implementation of the mapping approach (single-bead limit). Being based on trajectories, the method scales well with the number of degrees of freedom and will be applicable to simulate certain nonadiabatic processes in complex molecular systems.