First Principles Calculations of Binary Alloy Phase Diagrams

Abstract

In the past decade attempts to obtain a theoretical knowledge of thermodynamic data and phase diagrams of alloys have been made by combining, at a high level of accuracy, both quantum-mechanical and statistical-thermodynamical contributions. These calculations have to take into account the local chemical environment in the alloy which is important in determining both the internal energy and the entropy of configuration. One of the most efficient methods for including short and long range order is the cluster variation method. This method needs, as input the effective cluster interactions which determine ordering or clustering reactions occurring in a given lattice. These interactions can be derived from experimental data such as critical temperatures or enthalpies of formation, but they can also be obtained within the tightbinding framework or by using purely “ab-initio” methods such as the linear muffin tin orbitals. These methods are presented and the results obtained in binary metallic alloys are reported.