Energetics of alloy formation within statistical thermodynamics and electron theory

The deviation of the thermo-physical functions from the additive rule of mixing as a function of composition, temperature, and pressure is a key to an understanding of the energetics of alloy formation. The implications of the basic interactions of the metallic system i.e. electron-electron, ion-ion and electron-ion on formation energy are discussed within the first principle approach of the electronic theory. The pairwise interactions calculated from the first principle theory, coupled with pair distribution functions, provide a unique definition of the order energy which occurs as a free parameter in various thermodynamic models. The solution of the grand partition function within quasi-lattice approximation, and the hard sphere results modified for attractive tail interaction, are also considered to discuss the effects of entropic and enthalpic contributions on formation energy. It is observed that the basic principles underlying these distinct theoretical approaches complement each other.