Introduction

Abstract

Abstract This book was written in order to replace two second-year undergraduate courses that used to be taught in the Department of Materials at Oxford University on free electron theory and band theory. Those courses considered the electronic structure of perfect crystals and exploited the translational symmetry of perfect crystals to set the problem up in reciprocal space. It was recognized that they did not serve the needs of a modern degree in materials science. Modern materials science is at least as concerned with defects in crystals and noncrystalline materials as it is with the properties of perfect crystals. (In a phrase often attributed to F. C Frank ‘crystals are like people-it is the defects in them that make them interesting’.) Band theory and free electron theory have very little to say about such things, because they rely on perfect translational symmetry and Bloch’s theorem.