Semiclassical Dynamics in Wigner Phase Space II : nonadiabatic Hybrid Wigner Dynamics

TL;DR

This paper introduces a nonadiabatic hybrid Wigner dynamics framework that combines semiclassical and quantum methods to efficiently simulate complex quantum systems with mixed degrees of freedom.

Contribution

It extends previous hybrid Wigner dynamics to nonadiabatic processes with two variants, improving accuracy for systems with strongly coupled nuclear modes.

Findings

NHWD(E) is accurate for many scattering and spin-boson models.

NHWD(V) captures long-time dynamics in systems with strongly coupled nuclear modes.

The framework enables semiclassical simulations of high-dimensional quantum systems.

Abstract

We present an approximate semiclassical (SC) framework for mixed quantized dynamics in Wigner phase space in a two-part series. In the first article, we introduced the Adiabatic Hybrid Wigner Dynamics (AHWD) method that allows for a few important `system' degrees of freedom to be quantized using high-level Double Herman-Kluk SC theory while describing the rest (the `bath') using classical-limit Linearized SC theory. In this second article, we extend our hybrid Wigner dynamics to nonadiabatic processes. The resulting Nonadiabatic Hybrid Wigner Dynamics (NHWD) has two variants that differ in the choice of degrees of freedom to be quantized. Specifically, we introduce NHWD(E) where only the electronic state variables are quantized and the NHWD(V) where both electronic state variables and a handful of strongly coupled nuclear modes are quantized. We show that while NHWD(E) proves accurate for a wide range of scattering models and spin-boson models, systems where a few nuclear modes are strongly coupled to electronic states require NHWD(V) to accurately capture the long-time dynamics. Taken together, we show that AHWD and NHWD represent a new framework for SC simulations of high-dimensional systems with significant quantum effects.