  In this study, an efficient first-principles approach for calculating the
thermodynamic properties of mixed metal oxides at high temperatures is
demonstrated. More precisely, this procedure combines density functional theory
and harmonic phonon calculations with tabulated thermochemical data to predict
the heat capacity, formation energy, and entropy of important metal oxides.
Alloy cluster expansions are, moreover, employed to represent phases that
display chemical ordering as well as to calculate the configurational
contribution to the specific heat capacity. The methodology can, therefore, be
applied to compounds with vacancies and variable site occupancies. Results are,
moreover, presented for a number of systems of high practical relevance:
Fe-K-Ti-O, K-Mn-O, and Ca-Mn-O. In the case of ilmenite (FeTiO3), the agreement
with experimental measurements is exceptionally good. When the generated data
is used in multi-phase thermodynamic calculations to represent materials for
which experimental data is not available, the predicted phase-diagrams for the
K-Mn-O and K-Ti-O systems change dramatically. The demonstrated methodology is
highly useful for obtaining approximate values on key thermodynamic properties
in cases where experimental data is hard to obtain, inaccurate or missing.
