SYNTHESIS AND STRUCTURE DETERMINATION OF SM3NBSE3O4

Sm3NbSe3O4 has been synthesized and its structure determined. The foll owing crystal data were obtained: M-r = 844.84 g . mol(-1), orthorhomb ic, Pnma, a = 6.8943(4) Angstrom, b = 7.7529(8) Angstrom, c = 14.7644( 12) Angstrom, V = 789.2(1) Angstrom(3), Z = 4, D-x = 7.111 g . cm(-3), MoK alpha, lambda = 0.71073 Angstrom, mu = 372 cm(-1), F(000) = 1444, T = 295 K, R = 0.035 for 1466 unique reflections with F-0 > 4 sigma(F -0), 62 variables, GoF = 0.818. The structure of Sm3NbSe3O4 was determ ined by single-crystal X-ray diffraction. Two distinct types of polyhe dra can be distinguished: a very distorted one with eight surrounding atoms (four O and four Se atoms) around Sm1 and Nb, and a bicapped tri gonal prismatic one around Sm2. The crystal structure of this new comp ound can be described on the basis of corrugated planes perpendicular to the c axis. These planes are built up from edge-sharing trigonal pr ismatic polyhedra (Sm2); connection between successive planes is achie ved through the distorted polyhedra which surround atoms Sm1 and Nb. ( C) 1998 Academic Press.