Exact Factorization Adventures: A Promising Approach for Non-bound States

TL;DR

This paper reviews the exact factorization approach for modeling non-bound molecular states, highlighting its ability to accurately incorporate electronic-nuclear coupling and exploring various approximation methods and their implications.

Contribution

It introduces and compares different XF-based mixed quantum-classical methods, including coupled and auxiliary trajectory approaches, for simulating molecular dissociation.

Findings

Coupling terms significantly influence dissociation dynamics.

Auxiliary trajectories can effectively mimic true coupling effects.

Different XF-based approximations impact the accuracy of quantum-classical simulations.

Abstract

Modeling the dynamics of non-bound states in molecules requires an accurate description of how electronic motion affects nuclear motion and vice-versa. The exact factorization (XF) approach offers a unique perspective, in that it provides potentials that act on the nuclear subsystem or electronic subsystem, which contain the effects of the coupling to the other subsystem in an exact way. We briefly review the various applications of the XF idea in different realms, and how features of these potentials aid in the interpretation of two different laser-driven dissociation mechanisms. We present a detailed study of the different ways the coupling terms in recently-developed XF-based mixed quantum-classical approximations are evaluated, where either truly coupled trajectories, or auxiliary trajectories that mimic the coupling are used, and discuss their effect in both a surface-hopping framework as well as the rigorously-derived coupled-trajectory mixed quantum-classical approach.