  A novel mixed quantum-classical approach to simulating nonadiabatic dynamics
of molecules at metal surfaces is presented. The method combines the
numerically exact hierarchical equations of motion approach for the quantum
electronic degrees of freedom with Langevin dynamics for the classical degrees
of freedom, namely, low-frequency vibrational modes within the molecule. The
approach extends previous mixed quantum-classical methods based on Langevin
equations to models containing strong electron-electron or quantum
electronic-vibrational interactions, while maintaining a nonperturbative and
non-Markovian treatment of the molecule-metal coupling. To demonstrate the
approach, nonequilibrium transport observables are calculated for a molecular
nanojunction containing strong interactions.
