Synthesis and crystal structure of the binary molybdate Li8Bi2(MoO4)7

Abstract

Single crystals of Li8Bi2(MoO4)7 were synthesized; the composition and crystal structure of this compound were determined from X-ray diffraction data (CAD-4 automatic diffractometer, MoKa radiation, 1767 reflections, R = 0.031). The parameters of the tetragonal unit cell are as follows: a = 21.130, c = 5.287 A, Z = 4, space group -14. The structure of the binary molybdate is a three-dimensional mixed framework of MoO4 tetrahedra of four varieties, Bi eight-vertex potyhedra, and Li(l)O6 and Li(2)O6 octahedra. The large channels of the framework along the c axis contain MoO4 tetrahedra of the fifth variety with Li(3)O4 and Li(4)O4 tetrahedra attached to them via common vertices and forming four symmetrically related chains of pyroxene type. The structure of Li8Bi2(MoO4)7 involves structural fragments of Li3Fe(MoO4)3 and a-RbPr(MoO4)2 and is a new structural type in the class of binary molybdates and tungstates of uniand trivalent metals.