Structure and phase stability of alloys based on systematic first principles thermodynamics calculations

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Statistical thermodynamics plays a crucial role in modern materials science. The free energy of compounds is indispensable for discussing the phase stability. In general, a number of phenomena contribute to the temperature dependence of the free energy. In multicomponent systems, an important contribution to the free energy arises from the atomic configuration. The configurational effects have been estimated by density functional theory calculations and the cluster expansion method. Therefore, methodologies for computing the configurational properties, based on DFT calculations and the CE method, are proposed. We have constructed ground state structures and phase diagrams for a pseudobinary MgO-ZnO and MgO-NiO systems. In addition, the average structure at a finite temperature has been estimated by carrying out first-principles molecular dynamics calculations.