Constructing a Model for Gamma-Alumina

Aluminum is widely used throughout industry, research, and development as its oxidized form alumina. In fact, alumina rapidly forms on the surface of aluminum, which makes its properties potentially important to any system with aluminum. Alumina has many phases, and one that is of interest at high temperatures for devices from catalytic converters to hydrogen separation systems is gamma-alumina. The importance of accurate simulations for the optimization of its chemical properties requires an accurate structure of gamma-alumina. Experimental evidence indicates that the structure is a spinel with aluminum vacancies at tetrahedral sites along planar defects. Crystallographic analysis has provided the details for inserting a single defect into a crystal. However, simulation requires many defects in complex arrangements. This report introduces a detailed method for constructing a periodic crystal of gamma-alumina consistent with experimental results and appropriate for simulation. Some important symmetries of the defects and other simulation considerations are also discussed. The MATLAB code implementing the method and an example of its use are provided.