Multiconfigurational Ehrenfest approach to quantum coherent dynamics in large molecular systems

Abstract

This article briefly describes recently developed Multiconfigurational Ehrenfest dynamics method to simulate quantum dynamics in systems with many degrees of freedom. The central idea is to guide the trajectories of basis wave functions by means of the Ehrenfest trajectories. The amplitudes of guided basis functions are coupled through a system of linear equations. The approach has been applied to simulations of nonadiabatic dynamics in Spin–Boson model and in pyrazine molecule. A new application to nonadiabatic dynamics in 24D model of pyrazine, where good spectrum for is obtained with the basis of only 34 basis Ehrenfest configurations is reported. This application provides the ground for future fully quantum direct dynamics. Another new application to the model of sticking to the surface described by the System-Bath Hamiltonian is presented to demonstrate the broadness of the approach, which can be applied to both electronically adiabatic and nonadiabatic dynamics. For all applications the results are in good agreement with those of MCTDH, which is very difficult to achieve with other trajectory-based methods. Therefore MCE can serve as a starting point for future use with “on the fly” direct dynamics. MCE provides an efficient fully quantum method capable of catching coherent dynamics in multidimentional systems, which is a necessary step for developing and understanding coherent control in realistic quantum systems.