CRYSTAL-STRUCTURE OF SHOMIOKITE-(Y), NA3Y(CO3)(3)3H(2)O

Shomiokite, Na3Y(CO3)(3) 3H(2)O, M = 391.9, orthorhombic, space group Pna2(1), a = 17.358(8), b = 10.034(4), c = 5.946 (2) Angstrom, V = 103 5.6 Angstrom(3), Z = 4, rho(o) = 2.52, rho(c) = 2.51 g/cm(3), lambda(M oK alpha) = 0.71073 Angstrom, mu = 60.2 cm(-1), dimensions (mm) 0.25 x 0.1 x 0.1, F(000) = 768, room temperature, R = 0.059 for 1973 reflect ions with \F\ > 3 sigma(F). The structure contains isolated mixed comp lexes, formed by YO9 polyhedra, which share three edges with CO3 group s. The mixed complexes are considered as relicts of corrugated polyhed ral layers, described in tengerite, kimuraite and lokkaite, and are co nnected through distorted Na octahedra, 5-fold polyhedra and a system of H-bonds.