On decoherence in surface hopping: the nonadiabaticity threshold

TL;DR

This paper introduces a threshold-based decoherence correction for surface hopping that improves accuracy by limiting decoherence to regions of low nonadiabaticity, applicable across various systems.

Contribution

It proposes a simple, general strategy to improve decoherence modeling in surface hopping by using a nonadiabaticity threshold, enhancing accuracy and applicability.

Findings

Gaussian overlap correction yields better populations than no correction.

Threshold-based decoherence is effective across different systems.

Instantaneous decoherence is appropriate under specific conditions.

Abstract

This work presents a strategy to efficiently and safely account for decoherence in the fewest switches surface hopping method. Standard decoherence corrections often lead to too strong coherence suppression. A simple and general solution to this problem is to restrict decoherence to regions of low nonadiabaticity measured by the dimensionless Massey parameter. The same threshold values are suitable for a variety of systems, regardless of their size and absolute energy scale. When restricted to uncoupled regions, a Gaussian overlap decoherence correction consistently leads to more accurate populations than using no correction. The article also examines under what circumstances it is appropriate to decohere instantaneously.