Robust non-adiabatic molecular dynamics for metals and insulators

TL;DR

This paper introduces an improved correlated electron-ion dynamics method that accurately simulates non-adiabatic electronic transitions in metals and insulators by including quantum fluctuations and ensuring conservation laws.

Contribution

The paper develops a new CEID formulation with a single tunable parameter, enhancing accuracy and applicability for modeling non-adiabatic dynamics in complex systems.

Findings

Demonstrates convergence to exact dynamics in a two-level model

Ensures conservation of energy and momentum during simulations

Preserves quantum coherence in non-adiabatic processes

Abstract

We present a new formulation of the correlated electron-ion dynamics (CEID) scheme, which systematically improves Ehrenfest dynamics by including quantum fluctuations around the mean-field atomic trajectories. We show that the method can simulate models of non-adiabatic electronic transitions, and test it against exact integration of the time-dependent Schroedinger equation. Unlike previous formulations of CEID, the accuracy of this scheme depends on a single tunable parameter which sets the level of atomic fluctuations included. The convergence to the exact dynamics by increasing the tunable parameter is demonstrated for a model two level system. This algorithm provides a smooth description of the non-adiabatic electronic transitions which satisfies the kinematic constraints (energy and momentum conservation) and preserves quantum coherence. The applicability of this algorithm to more complex atomic systems is discussed.