Short-range order and superstructures of ternary oxides AMO₂, A₂MO₃ and A₅MO₆ of monovalent A and multivalent M metals related to the NaCl structure

Ternary oxides AMO₂, A₂MO₃ and A₅MO₆ with monovalent A and tri-, tetra- or hepta-valent M metals can exhibit order/disorder transitions with about 20 superstructures of the NaC1 lattice. Some structures can be related to AM, A2M and A₅M alloys with a larger distortion of the lattice due to stronger interactions between metal atoms. In ternary oxides about 30 short-range order configurations are selected for the first, second and third shell of metal atoms in applying Pauling's electrovalence rule. Stable configurations are characterized by the strength of Coulomb interactions and by a high point symmetry of the M atoms. Mainly disordered ternary oxides can vary stoichiometrically with a frequent occurrence of vacancies or with partial occupation of tetrahedral interstices by A atoms.