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

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-Tc 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-Tc properties of these materials are discussed.