Prediction of ground-state structures and order-disorder phase transitions in II-III spinel oxides: A combined cluster-expansion method and first-principles study

Abstract

Ground-state structures of six II-III spinel oxides are predicted by combining the cluster expansion method and first principles calculations. The ground states of $\mathrm{Mg}{\mathrm{Ga}}_{2}{\mathrm{O}}_{4}$ and $\mathrm{Mg}{\mathrm{In}}_{2}{\mathrm{O}}_{4}$ are found to be inverse spinels with a tetragonal lattice, whereas those of $\mathrm{Mg}{\mathrm{Al}}_{2}{\mathrm{O}}_{4}$, $\mathrm{Zn}{\mathrm{Al}}_{2}{\mathrm{O}}_{4}$, $\mathrm{Zn}{\mathrm{Ga}}_{2}{\mathrm{O}}_{4}$, and $\mathrm{Zn}{\mathrm{In}}_{2}{\mathrm{O}}_{4}$ are normal spinels with a cubic lattice. Order-disorder transition behaviors are examined using Monte Carlo simulations. The order-disorder transition to exchange octahedral and tetrahedral cations takes place as commonly accepted. In inverse spinels, a new kind of transition to exchange II and III cations in octahedral sites can be recognized, which has not been reported experimentally. Their transition temperatures are evaluated.