# Comparison of aluminum oxide empirical potentials from cluster to nanoparticle

## TL;DR

This study evaluates four empirical potentials for aluminum oxide, identifying two that accurately model phase transitions from amorphous to crystalline states at nanoscale, aligning with experimental observations.

## Contribution

It compares and validates empirical potentials for alumina across different scales, highlighting the most reliable ones for simulating phase transitions.

## Key findings

- Two potentials accurately match DFT calculations at the molecular level.
- The two selected potentials reproduce key phase transitions observed experimentally.
- Only two of the four potentials are suitable for nanoscale alumina simulations.

## Abstract

Aluminum oxide nanoparticles are increasingly sought in numerous technological applications. However, as the nanoparticles grow during the synthesis, two phase transitions occur. At the nanoscale, numerical simulation of the stability of the alumina phases requires the use of empirical potentials that are reliable over a large range of system sizes going from a few atoms to several hundred thousand atoms. In this work, we confronted four different empirical potentials that are currently employed for bulk alumina. We found that only two of them are correct at the molecular level when compared to DFT calculations. Furthermore, the two potentials remain the best at the nanoscale as they reproduce one or two phase transitions that were observed experimentally: from amorphous solid to cubic crystal ({\gamma}) and from cubic to hexagonal ({\alpha}, i.e. corundum) crystal.