# Minimally-corrected partial atomic charges for non-covalent electrostatic interactions

## TL;DR

This paper introduces a new method for refining molecular partial atomic charges by making minimal corrections to existing reference PACs, resulting in improved electrostatic potential reproduction while maintaining symmetry invariance.

## Contribution

The authors develop a minimally-corrected PAC scheme that enhances ESP accuracy and preserves molecular symmetry, applicable to various reference charge sets.

## Key findings

- MC-PACs significantly improve ESP reproduction.
- MC-PACs preserve reference PACs' symmetry invariance.
- Comparable ESP quality to ChElPG method when using iterative-Hirshfeld PACs.

## Abstract

We develop a new scheme for determining molecular partial atomic charges (PACs) with external electrostatic potential (ESP) closely mimicking that of the molecule. The PACs are the "minimal corrections" to a reference-set of PACs necessary for reproducing exactly the tensor components of the Cartesian zero- first- and second- molecular electrostatic multipoles. We evaluate the quality of ESP reproduction when "minimally correcting" (MC) Mulliken, Hirshfeld or iterated-Hirshfeld reference PACs. In all these cases the MC-PACs significantly improve the ESP while preserving the reference PACs' invariance under the molecular symmetry operations. When iterative-Hirshfeld PACs are used as reference the MC-PACs yield ESPs of comparable quality to those of the ChElPG charge fitting method.