# A fractionally ionic approach to polarizability and van der Waals many-body dispersion calculations

## TL;DR

This paper introduces a novel method that explicitly incorporates fractional ionic contributions to improve the accuracy of polarizability and van der Waals many-body dispersion calculations, especially in ionic and nanotechnological systems.

## Contribution

It presents a fractionally ionic approach that enhances existing atom-wise many-body van der Waals methods with minimal additional computational cost.

## Key findings

- Significantly improves polarizability predictions in ionic solids by over 65%.
- Achieves comparable accuracy to existing methods for non-ionic systems.
- Provides better modeling of two-dimensional transition metal dichalcogenides and H₂ interactions with modified coronenes.

## Abstract

By explicitly including fractionally ionic contributions to the polarizability of a many-component system we are able to significantly improve on previous atom-wise many-body van der Waals approaches with essentially no extra numerical cost. For non-ionic systems our method is comparable in accuracy to existing approaches. However, it offers substantial improvements in ionic solids, e.g. producing better polarizabilities by over 65% in some cases. It has particular benefits for two-dimensional transition metal dichalcogenides, and interactions of H$_2$ with modified coronenes - ionic systems of nanotechnological interest. It thus offers an efficient improvement on existing approaches, valid for a wide range of systems.