Computer Modelling of Oxide Surfaces and Interfaces

Abstract

The aim of this article is to describe an approach for modelling the structures and energetics of surfaces and interfaces of inorganic solids using computer simulation techniques. The wide range of applications of these methods on surfaces and grain boundaries has recently been reviewed by Mackrodt [1]. Much of this work has been confined to the cubic rocksalt oxides MgO, CaO and NiO [2,3], and only recently has been extended to more complicated materials such as UO₂[4] and α-Al₂O₃[5]. We will illustrate the application of these techniques by considering both perfect surfaces and point defects at surfaces in the corundum-structured oxides. The principal surface defects we shall consider are impurities as they are of fundamental importance in determining the properties of the materials i.e. impurities will affect sintering, densification and the catalytic properties of the materials [6,7,8]. A comprehensive knowledge of the effects of impurity level concentrations on behaviour is therefore of critical importance in the design and implementation of technologically important materials and processes. The advent and improvement of surface sensitive optical techniques such as AES, SEM and LEED has allowed more extensive experimental investigations of the role of impurities to take place. These techniques can now be coupled with theoretical calculations using static simulation methods to give a better picture of the effects of both iso- and aliovalent impurities on ceramic surfaces.