Title: Path integral molecular dynamics with surface hopping for thermal equilibrium sampling of nonadiabatic systems,
Abstract: In this work, a novel ring polymer representation for multi-level quantum
system is proposed for thermal average calculations. The proposed presentation
keeps the discreteness of the electronic states: besides position and momentum,
each bead in the ring polymer is also characterized by a surface index
indicating the electronic energy surface. A path integral molecular dynamics
with surface hopping (PIMD-SH) dynamics is also developed to sample the
equilibrium distribution of ring polymer configurational space. The PIMD-SH
sampling method is validated theoretically and by numerical examples.