Including nuclear quantum effects in mixed-quantum classical non-adiabatic dynamics

Abstract

We describe a path-integral approach for including nuclear quantum effects in non-adiabatic chem. Dynamics simulations. For a general phys. system with multiple electronic energy levels, a corresponding isomorphic Hamiltonian is introduced, such that Boltzmann sampling of the isomorphic Hamiltonian with classical nuclear degrees of freedom yields the exact quantum Boltzmann distribution for the original phys. system. In the limit of a single electronic energy level, the isomorphic Hamiltonian reduces to the familiar cases of either ring polymer mol. dynamics (RPMD) or centroid mol. dynamics Hamiltonians, depending on implementation. An advantage of the isomorphic Hamiltonian is that it can easily be combined with existing MQC dynamics methods, such as surface hopping or Ehrenfest dynamics, to enable the simulation of electronically non-adiabatic processes with nuclear quantum effects.