CRYSTAL-CHEMISTRY OF CD2-XCUXP2O7, 0-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-2 STRUCTURE OF CDCUP2O7

The domains of the system, Cd2-xCuxP2O7, O less-than-or-equal-to x less-than-or-equal-to 2, have been established by powder diffraction methods. Two solid solutions have been found near Cd2P2O7 (0 less-than-or-equal-to X less-than-or-equal-to 0.40) and Cu2P2O7 (1.60 less-than-or-equal-to x less-than-or-equal-to 2). A new phase with x = 1 has been identified using single crystal X-ray diffraction. The mixed diphosphate CdCuP2P7 (x = 1) crystallizes in monoclinic space group C2 with a = 6.806(7), b = 8.665(4), c = 4.504(2) angstrom, beta = 105.85(6)-degrees, V = 255.5(3) angstrom3, lambda(MoKalpha) = 0.71069 angstrom, mu(MoKalpha) = 89.26 cm-1, D(calc) = 4.55 g cm-3, D(meas) = 4.59(5) g cm-3, Z = 2, F(000) = 326, T = 298 K, R = 3.9%, R(W) = 5. 1% for 247 observed reflections. P2O7 groups show staggered conformation identifying the solid state structure to be of the thortveitite type. The mixed Cd:Cu sites display sixfold coordination with average M-O distance 2.24(3) angstrom. (C) Academic Press, Inc.