# Application of Ewald summations to long-range dispersion forces

## TL;DR

This paper investigates the impact of explicitly summing long-range dispersion forces using Ewald summations on the properties of Lennard-Jones fluids and SPC/E water, highlighting the importance of system size and interaction type.

## Contribution

It demonstrates that long-range dispersion summations can produce results consistent with large cutoff simulations and clarifies their secondary role compared to Coulombic forces in water.

## Key findings

- Long-range summations yield consistent results with large cutoff simulations.
- Dispersion forces are less significant than Coulombic forces in water.
- Box size to crossover radius ratio influences dispersion correction magnitude.

## Abstract

We present results illustrating the effects of using explicit summation terms for the $r^{-6}$ dispersion term on the interfacial properties of a Lennard-Jones fluid and SPC/E water. For the Lennard-Jones fluid, we find that the use of long-range summations, even with a short ``crossover radius,'' yields results that are consistent with simulations using large cutoff radii. Simulations of SPC/E water demonstrate that the long-range dispersion forces are of secondary importance to the Coulombic forces. In both cases, we find that the ratio of box size $L_{\parallel}$ to crossover radius $r_{\rm c}^{\mathbf k}$ plays an important role in determining the magnitude of the long-range dispersion correction, although its effect is secondary when Coulombic interactions are also present.