Computer modeling of the local structure, mixing properties, and stability of solid solutions of alkaline-earth metal oxides

A technique for the computer modeling of disordered binary oxide solid solutions MO-M′O in a wide composition range has been developed. The method of atomistic pair potentials was used for 4 × 4 × 4 supercells. The parameters of the potentials are optimized using the structural and elastic properties of pure components MgO, CaO, SrO, and BaO. The temperature dependences of the heat capacity and entropy are calculated for pure components. The excess mixing properties (enthalpy, volume, bulk modulus, vibrational entropy) are found for different compositions of Mg _x Ca_{(1 ? x)}O, Ca _x Sr_{(1 ? x)}O, and Sr _x Ba_{(1 ? x)}O solid solutions. Temperature and composition dependences of the excess Gibbs energy were constructed, which made it possible to approximately estimate the critical decomposition temperatures and limits of component miscibility. Statistical analysis of lattice distortions in the first and second coordination spheres reveals a detailed picture of the solid-solution local structure.