The crystal structure of beta strontium pyrovanadate

Abstract

β-Sr2V2O7 is tetragonal, space group P41 with eight formula units per unit cell and a = 7.055(2), Å, c = 25.64(2), Å. The compound is isomorphous with β-Ca2P2O7. The structure was determined from three-dimensional data collected on an automatic diffractometer with both CuKα and MoKα radiation. It was solved by comparing a Patterson section at z = 1 2 with a difference Fourier map. The phases for the latter were calculated from the Ca and P coordinates of β-Ca2P2O7. The oxygen atoms were subsequently located from successive difference Fourier maps, and the structure was refined by full-matrix least squares with isotropic temperature factors. The two different sets of data were refined separately, and the final R is 0.058 and 0.046 for data using Cu and Mo radiation, respectively. The compound has the dichromate-type structure with nearly eclipsed V2O7 groups. The bond distances for the two independent pyrovanadate anions are separable into two sets: the bridging bonds whose lengths are ∼1.81 Å and the nonbridging bonds whose lengths range between 1.63 - 1.77 Å. The {A figure is presented} bond angles are 123°. The coordination number of strontium ranges from 7 to 9. © 1972.