# Bonding of Cobalt Atoms, Dimers and Co$_4$ Clusters to Circumcoronene

## TL;DR

This study investigates how cobalt atoms, dimers, and clusters interact with circumcoronene, revealing preferred bonding sites, structural arrangements, magnetic effects, and charge transfer characteristics.

## Contribution

It provides detailed insights into the bonding configurations, magnetic properties, and charge transfer phenomena of cobalt clusters on circumcoronene, a topic not extensively explored before.

## Key findings

- Cobalt prefers hollow edge sites on circumcoronene.
- Cobalt dimers bond perpendicularly to hollow sites.
- Co4 clusters adopt a tetrahedral shape with specific bonding arrangements.

## Abstract

We study the interaction of circumcoronene molecule C$_{54}$H$_{18}$ with cobalt in the form of atoms, dimers and clusters of four atoms. We find that the cobalt atom prefers to be on a hollow site in the edge zone. The cobalt dimer is bonded perpendicularly to another different hollow site in the edge zone. The Co$_{4}$ cluster adopts a tetrahedral shape with a face parallel to circumcoronene, placing each of the three atoms over contiguous hollow sites, starting from the edge. Cobalt remains bonded to circumcoronene as Co$_{2}$ molecules or Co$_{4}$ clusters, rather than spread as isolated atoms, because the cobalt-cobalt interaction is stronger than the cobalt-carbon one. However, the interaction with cobalt clusters induce small magnetic moment on circumcoronene. The magnetic moment of cobalt counterpart is reduced when it is bonded to circumcoronene. There is charge transfer between those systems and its direction depends on the relative position of the cluster with respect to circumcoronene.