Spontaneous Formation of Dipolar Metal Nanoclusters

TL;DR

This study uses density functional theory to explore how silver clusters form dipolar structures on alumina surfaces, revealing simultaneous ionic and intermetallic bonds that could impact catalysis.

Contribution

It introduces the concept of dipolar nanoclusters formed by silver on alumina, showing coexistence of different bonding motifs within a single nanoparticle.

Findings

Silver clusters form both ionic and intermetallic bonds on alumina.

The coexistence of bonding types is due to similar bond enthalpies.

Dipolar nanoclusters may influence catalytic properties.

Abstract

The adsorption of Ag$_3$ and Ag$_4$ clusters on the $\alpha$-Al$_2$O$_3$(0001) surface is explored with density functional theory. Within each adsorbed cluster, two different cluster-surface interactions are present. We find that silver clusters simultaneously form both ionic bonds with surface oxygen and intermetallic bonds with surface aluminum. The simultaneous formation of disparate electronic structure motifs within a single metal nanoparticle is termed a "dipolar nanocluster". This coexistence is ascribed to the similar bond enthalpies of Ag--Al and Ag--O bonds, and its importance for nanoparticle catalysis is highlighted.