Structural parameters and electron difference density in BaTiO₃

Abstract

Diyttrium barium copper(II) pentoxide, Y2BaCuOs, Mr=458.7, orthorhombic, Pnma, a = 12.188 (2), b = 5.662 (2), c = 7.132 (2)/~, V= 492.17 (3) ,~3, Z = 4, Dx = 6.19 Mg m-3, a(Mo Ka) = 0.71069 ,~,, /1, = 36.633 mm-I, F(000) = 812, T= 298 K, final R = 0.059, wR = 0.028 for 2758 unique reflections. The structural parameters for the nonsuperconducting 'green phase' YzBaCuOs were redetermined and the electron density compared with that for the high-To superconductor YBa2Cu3OT-6. The zip topography near Cu in Y2BaCuO5 resembles that near Cu2 in YBa2Cu3Ov_~, which has similar coordination. It differs markedly from that near Cul, which coordinates with disordered O atoms. The similarity of both coordination and electron density for the Cu atom in the green phase with those for Cu2 in the high-T,, compound is consistent with both atoms being in the + 2 oxidation state.