Beyond Born-Mayer: Improved models for short-range repulsion in ab initio force fields

TL;DR

This paper introduces a new short-range repulsion model for ab initio force fields based on a Slater-like density approach, improving accuracy and transferability over traditional Lennard-Jones and Born-Mayer models.

Contribution

It develops a novel functional form derived from atomic density overlaps and ISA partitioning, enhancing the description of short-range interactions in force fields.

Findings

The Slater-ISA model outperforms traditional models in accuracy.

The new approach maintains computational efficiency.

It can be adapted to replicate the Born-Mayer form.

Abstract

Short-range repulsion within inter-molecular force fields is conventionally described by either Lennard-Jones (${A}/{r^{12}}$) or Born-Mayer ($A\exp(-Br)$) forms. Despite their widespread use, these simple functional forms are often unable to describe the interaction energy accurately over a broad range of inter-molecular distances, thus creating challenges in the development of ab initio force fields and potentially leading to decreased accuracy and transferability. Herein, we derive a novel short-range functional form based on a simple Slater-like model of overlapping atomic densities and an iterated stockholder atom (ISA) partitioning of the molecular electron density. We demonstrate that this Slater-ISA methodology yields a more accurate, transferable, and robust description of the short-range interactions at minimal additional computational cost compared to standard Lennard-Jones or Born-Mayer approaches. Finally, we show how this methodology can be adapted to yield the standard Born-Mayer functional form while still retaining many of the advantages of the Slater-ISA approach.