Quasi-Diabatic Representation for Nonadiabatic Dynamics Propagation.

We develop a nonadiabatic dynamics propagation scheme that allows interfacing diabatic quantum dynamics methods with commonly used adiabatic electronic structure calculations. This scheme uses adiabatic states as the quasi-diabatic (QD) states during a short-time quantum dynamics propagation. At every dynamical propagation step, these QD states are updated based on a new set of adiabatic basis. Using the partial linearized density matrix (PLDM) path-integral method as one specific example for diabatic dynamics approaches, we demonstrate the accuracy of the QD scheme with a wide range of model nonadiabatic systems as well as the on-the-fly propagations with density functional tight-binding (DFTB) calculations. This study opens the possibility to combine accurate diabatic quantum dynamics methods with adiabatic electronic structure calculations for nonadiabatic dynamics propagations.