Total Angular Momentum Conservation in Ab Initio Born-Oppenheimer Molecular Dynamics

TL;DR

This paper demonstrates that total angular momentum conservation in Born-Oppenheimer molecular dynamics depends on including Berry forces, revealing their role in accurately capturing spin-nuclear entanglement in molecular systems.

Contribution

It provides an analytical and numerical proof that Berry forces are essential for angular momentum conservation in ab initio Born-Oppenheimer dynamics.

Findings

Angular momentum conservation depends on Berry forces.

Berry forces are crucial for systems with spin-orbit coupling.

Simulations can capture spin-nuclear entanglement through Berry forces.

Abstract

We prove both analytically and numerically that the total angular momentum of a molecular system undergoing adiabatic Born-Oppenheimer dynamics is conserved only when pseudo-magnetic Berry forces are taken into account. This finding sheds light on the nature of Berry forces for molecular systems with spin-orbit coupling and highlights how ab initio Born-Oppenheimer molecular dynamics simulations can successfully capture the entanglement of spin and nuclear degrees of freedom as modulated by electronic interactions.