COPPER-CONTAINING MINERALS .1. CU3V2O7(OH)2, 2H2O - THE SYNTHETIC HOMOLOG OF VOLBORTHITE - CRYSTAL-STRUCTURE DETERMINATION FROM X-RAY AND NEUTRON DATA - STRUCTURAL CORRELATIONS

An ab initio structure determination of synthetic volborthite Cu3V2O7(OH)2, 2H2O was performed from X-ray and neutron powder data using a modified Rietveld method. The cell is monoclinic (space group C2/m; Z = 2) (X rays: a = 10.606(4) Å; b = 5.874(1) Å; c = 7.213(3) Å;β = 94.90(3)°) (neutrons: a = 10.607(5) Å; b = 5.864(4) Å; c = 7.214(6) Å; β = 94.88(4)°). The refinement leads to R1 = 0.035; Rp = 0.065; Rwp = 0.063 (X rays); and R1 = 0.060; Rp = 0.093; Rwp = 0.085 (neutrons). The structure is built up from defect brucite-type layers in the (001) plane, connected one to each other by pyrovanadate groups. The corresponding pillared and layered framework embeds water molecules. The hydrogen bonding subnetwork is described. Structural correlations are given. © 1990 Academic Press, Inc.