Computer modeling techniques are now widely used in all scientific disciplines. A particularly fruitful area of application is the field of materials science, where computational methods are now indispensable tools in studying the structure, properties and reactivities of materials. The field has expanded very rapidly in recent years owing both to the continuing exponential growth in hardware performance and the ongoing developments in techniques and algorithms. This book aims to give a survey of the fundamental methodologies and an illustrative range of contemporary applications. The field is now so large that the latter is necessarily selective, and our focus is on inorganic (especially oxide) materials and semiconductors, where there have been many important and exciting recent developments.