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Aluminium oxide is a hard material with high resistance to abrasion and compression and is highly resistant to chemical attack, even at elevated temperatures. It is also a good electrical insulator. Different types of aluminium oxide are used in a wide range of industrial applications including heavy-duty forming tools, resistor cores and substrates, wire guides for machinery and textiles, protective tubes for thermal processes and metering devices, tiles and abrasives. In addition, it is used in gem-quality corundum (rubies and sapphires), which owe their color to trace impurities.
In recent years, a number of studies have analysed the thermal properties of a-Al2O3 bulk materials in detail. The results are based on both MD simulations and experiments. Generally the reported values of the lattice constant and band gap are in excellent agreement with the experimental ones. However, the observed behaviour of the self-limiting oxidation is not always consistent.
The aim of this work is to understand the origin of these inconsistent observations. In particular, we use simulations to study the atomic dynamics of aluminium surface oxidation. In the simulations, a step-like behaviour of the aluminium atom deposition onto the oxygen-rich surface is observed. This is confirmed by the evolution of the density and stoichiometry, shown in Figs. 4 and 5. Moreover, by analysing the bond angle distribution in Fig. 6, the difference in the behaviour between the 77 K and 370 K calculations can be explained by the presence of a crystallisation phase in the low temperature calculations.