A comparison of the calculated lattice and defect structures of La₂CuO₄, La₂NiO₄, Nd₂CuO₄, Pr₂CuO₄, Y₂CuO₄, Al₂CuO₄: Relationship to high-T_c superconductivity

Abstract

Abstract This paper is concerned with the calculated static and dynamic lattice and defect properties of the ternary oxides, M2CuO4 (M = La, Pr, Nd, Y and Al) and La2, NiO4, with the principal aim of trying to understand why it is that apparently only M = La leads to high-temperature superconducting materials. Among the properties considered are the lattice structure, phonon density of states, fundamental defect structure, nature of the electronic disorder, oxidative non-stoichiometry and defect structure associated with alkaline-earth impurities. It is concluded that La2CuO4 has a unique combination of lattice and defect properties, which distinguishes it from the other materials considered, and which may be one of the reasons it exhibits high-Tc , behaviour, and that the only other ternary oxide of the same type that might exhibit similar behaviour is Nd2CuO4.