Rich Ground State Chemical Ordering in Nanoparticles: Exact Solution of a Model for Ag-Au Clusters

TL;DR

This paper demonstrates that nanoparticles can exhibit complex ground state chemical orderings, using an exact solution approach to analyze Ag-Au clusters with diverse structures and compositions.

Contribution

It introduces an exact solution method combining cluster expansion and MIP to determine ground state configurations of nanoparticles across all stoichiometries.

Findings

Nanoparticles show diverse and complex chemical orderings.

The method accurately finds ground states for all compositions.

Rich structural zoo observed in Ag-Au clusters.

Abstract

We show that nanoparticles can have very rich ground state chemical order. This is illustrated by determining the chemical ordering of Ag-Au 309-atom Mackay icosahedral nanoparticles. The energy of the nanoparticles is described using a cluster expansion model, and a Mixed Integer Programming (MIP) approach is used to find the exact ground state configurations for all stoichiometries. The chemical ordering varies widely between the different stoichiometries, and display a rich zoo of structures with non-trivial ordering.