Structural and defect properties of high-Tc oxides determined by atomistic lattice simulation

Abstract

Atomistic lattice simulations are used to study three sets of high-temperature superconducting cuprates. We concentrate on: (i) the crystal structure of the family of compounds RE₂MCu₂O₆(RE = La, Nd, Y; M = Ca, Sr, Ba); different members of this family have different cation orderings, and only those with divalent cations between the CuO₅ pyramids appear to give rise to high-T_c behaviour; (ii) the thermodynamic stability of the tetragonal ‘infinite-layer’ compounds MCuO₂(M = Mg, Ca, Sr, Ba), and the calculated defect chemistry of tetragonal CaCuO₂ and SrCuO₂; (iii) oxygen vacancy energies in YBa₂Cu₃O₇ and YBa₂Cu₄O₈. In each case the implications for the high-T_c properties of these materials are discussed.