Shifted forces in molecular dynamics

TL;DR

This paper compares two cut-off methods in Lennard-Jones molecular dynamics simulations, finding that the shifted forces cut-off allows for smaller cut-offs with accurate results, improving simulation efficiency.

Contribution

It demonstrates that the shifted forces cut-off method is superior for Lennard-Jones simulations, enabling smaller cut-offs without sacrificing accuracy.

Findings

Shifted forces cut-off at 1.5σ yields realistic results.

Shifted forces modifies Newton's equations at all distances.

Standard shifted potential cut-off has correct forces below cut-off.

Abstract

Simulations involving the Lennard-Jones potential usually employ a cut-off at $r=2.5\sigma$. This paper investigates the possibility of reducing the cut-off. Two different cut-off implementations are compared, the standard shifted potential cut-off and the less commonly used shifted forces cut-off. The first has correct forces below the cut-off, whereas the shifted forces cut-off modifies Newton's equations at all distances. The latter is nevertheless superior; we find that for most purposes realistic simulations may be obtained using a shifted-forces cut-off at $r=1.5\sigma$, even though the pair force is here 30 times larger than at $r=2.5\sigma$.