ND4CU2O7 - A COPPER(I) OXIDE WITH A NOVEL COOPERATIVELY DISTORTED T' TYPE-STRUCTURE

The crystal structure of Nd4Cu2O7 (monoclinic, space group A2/in, a = 8.4493(2) Angstrom, b = 3.7591(1) Angstrom, c = 12.6006(5) Angstrom, b eta = 109.576(4)degrees, Z= 2), prepared by topotactic reduction of th e high-T-c superconductor parent phase Nd2CuO4, has been determined by Rietveld fitting of time-of-flight neutron powder diffraction data (R -wp, = 1.90%). A novel oxygen-vacancy-ordered arrangement of cooperati vely distorted Cu2O3 planes containing 2- and I-coordinate Cu+ sites i s found. (C) 1998 Academic Press.