Balance, uniformity, and asymmetry of the structure of volborthite Cu3(OH)2(V2O7)·2H2O

Abstract

Four structural models of volborthite Cu3(OH)2(V2O7)·2H2O (a = 10.646(2) A, b = 5.867(1) A, c = 14.432(2) A, β = 95.19(1)°, V = 897.7(5) A3, Z = 4, R/R w = 0.038/0.046) calculated in the space groups determined from the systematic absences are compared. Based on the structure balance and the similarity of constituting polyhedra, values of the R factor, and isotropic thermal parameters, the space group Ia is found to be preferable, which is the only possible asymmetric and uniform variant. Hydrogen atoms of OH-groups, oxygen atoms and, partially, hydrogen atoms of water are localized.