Crystal stuctures of ScRe2Si3 and Sc3Re2Si3

The authors have determined the crystal structures of the compounds ScRe2Si3 (space group Amm2, a=14.486(3), b=5.2397(13) A, Z=16) and Sc3Re2Si3 (space group B2, a=19.604(6), b=13.741(5), c=5.339(1) A, β=125.92(2) 0, Z=8. The atomic parameters have been refined by the method of least squares (MLS) in the isotropic approximation to R=0.102 for 347 independent reflections (ScRe2Si3) and to R=0.092 for 740 independent reflections (Sc3Re2Si3). The reflection intensities have been measured on a Syntex P21 automatic diffractometer. The structures are assigned to new types. The coordination numbers in the structure of ScRe2Si3 are Sc 17, Re 14, 12, and 11, Si 10, 9, and 8; those in the structure of Sc3Re2Si3 are Sc 16 and 14, Re 12 and 11, Si 10 and 9. The coordination polyhedra of some of the Si atoms: deformed antiprisms: are typical of both structures; the other Si polyhedra are strongly deformed derivatives of trigonal prisms; one or two silicon atoms in ScRe2Si3 are located at the vertices of the prisms