PHASE DIAGRAMS AND BAND STRUCTURE OF TRANSITION METAL COMPOUNDS

Abstract

Phase diagrams and phase stabilities have in the past been dealt with using different approaches. In the Calphad method one seeks a description of the Gibbs energy function G(T) which is accurate enough to be used in calculations of phase diagrams for complex alloys. Ab initio electron band structure calculations, on the other hand, have been used to predict the cohesive properties of solids but such calculations are usually restricted to 0 K. We have combined these methods to get a better understanding of the phase stabilities. In particular we have critically analysed available thermodynamic information and used that together with band structure calculations to systematically discuss trends in the cohesive energy at 0 K and in the vibrational entropy. We have considered transition-metal carbides and nitrides, both in the NaCl and in more complex structures, and also transition-metal diborides.