Non-uniqueness of local stress of three-body potentials in molecular simulations

TL;DR

This paper investigates the non-uniqueness of local stress calculations in molecular simulations involving three-body potentials, proposing alternative force decompositions that conserve momentum and analyzing their impact on stress profiles.

Contribution

It introduces new force decomposition methods for three-body potentials that preserve physical conservation laws and compares their effects on stress distributions in simulations.

Findings

Different force decompositions yield varying stress profiles.

The proposed methods maintain conservation of momentum.

Stress distribution differences are significant in membrane simulations.

Abstract

Microscopic stress fields are widely used in molecular simulations to understand mechanical behavior. Recently, decomposition methods of multibody forces to central force pairs between the interacting particles have been proposed. Here, we introduce a force center of a three-body potential and propose different force decompositions that also satisfy the conservation of translational and angular momentum. We compare the force decompositions by stress-distribution magnitude and discuss their difference in the stress profile of a bilayer membrane using coarse-grained and atomistic molecular dynamics simulations.