Variational nonadiabatic dynamics in the moving crude adiabatic representation: Further merging of nuclear dynamics and electronic structure

TL;DR

This paper introduces a novel nonadiabatic dynamics simulation method that explicitly treats electron-nuclear interactions without relying on potential energy surface models, ensuring energy conservation and accurate dynamics near conical intersections.

Contribution

The new approach merges nuclear dynamics and electronic structure calculations using a moving crude adiabatic representation with on-the-fly electronic evaluations, eliminating the need for potential energy surface models.

Findings

Successfully reproduces nonadiabatic transition features

Handles geometric (Berry) phases accurately

Operates without uncontrolled approximations

Abstract

A new methodology of simulating nonadiabatic dynamics using frozen-width Gaussian wavepackets within the moving crude adiabatic representation with the on-the-fly evaluation of electronic structure is presented. The main feature of the new approach is elimination of any global or local model representation of electronic potential energy surfaces, instead, the electron-nuclear interaction is treated explicitly using the Gaussian integration. As a result, the new scheme does not introduce any uncontrolled approximations. The employed variational principle ensures the energy conservation and leaves the number of electronic and nuclear basis functions as the only parameter determining the accuracy. To assess performance of the approach, a model with two electronic and two nuclear spacial degrees of freedom containing conical intersections between potential energy surfaces has been considered. Dynamical features associated with nonadiabatic transitions and nontrivial geometric (or Berry) phases were successfully reproduced within a limited basis expansion.