ORDER AND DISORDER IN METALLIC ALLOYS

Self-consistent 'band theory', based on density functional theory, is a useful approach to describing the electron glue which holds solids together. However, its powerful group theoretic and numerical techniques cannot be deployed for disordered states of matter. The self-consistent KKR-CPA is an analogous method which is able to deal with some of these interesting cases. In particular, we show how it describes random metallic alloys, treating all the classic Hume-Rothery factors: size-effect, electronegativity and electrons per atom ratio (e:a) on more or less equal footing and from first principles. Moreover, we use the KKR-CPA framework to analyse the instability of the disorder state to compositional ordering processes and hence provide a first principle description of the forces which drive order-disorder transformations.