# Nonconventional screening of the Coulomb interaction in FexOy clusters: An ab-initio study

## TL;DR

This study uses ab-initio methods to analyze Coulomb interaction screening in FexOy clusters, revealing anti-screening effects in clusters unlike in bulk materials, with implications for understanding dimensionality effects.

## Contribution

It provides the first ab-initio evidence of anti-screening of intersite Coulomb interactions in FexOy clusters, contrasting with bulk behavior.

## Key findings

- Onsite Coulomb interaction is well screened in both clusters and bulk.
- Intersite Coulomb interaction remains nearly constant in clusters.
- Anti-screening of intersite Coulomb interaction observed in clusters.

## Abstract

From microscopic point-dipole model calculations of the screening of the Coulomb interaction in non-polar systems by polarizable atoms, it is known that screening strongly depends on dimensionality. For example, in one dimensional systems the short range interaction is screened, while the long range interaction is anti-screened. This anti-screening is also observed in some zero dimensional structures, i.e. molecular systems. By means of ab-initio calculations in conjunction with the random-phase approximation (RPA) within the FLAPW method we study screening of the Coulomb interaction in FexOy clusters. For completeness these results are compared with their bulk counterpart magnetite. It appears that the onsite Coulomb interaction is very well screened both in the clusters and bulk. On the other hand for the intersite Coulomb interaction the important observation is made that it is almost contant throughout the clusters, while for the bulk it is almost completely screened. More precisely and interestingly, in the clusters anti-screening is observed by means of ab-initio calculations.