THE CRYSTAL-STRUCTURE OF ORTHORHOMBIC CE3RH3SI2, AN INTERGROWTH OF FEB-TYPE AND YPD2SI-TYPE SLABS

The crystal structure of Ce,Rh,Si, was determined from single-crystal X-ray data (KM-4 automatic diffractometer, Mo K alpha radiation) and r efined to R-F= 0.0467 and R-W= 0.0417 for 1321 structure factors and 4 5 variable parameters. It is of a new type with orthorhombic symmetry: space group Pnma (No. 62), oP32, a = 7.722(2) Angstrom, b = 14.822(3) Angstrom, c = 5.759(1) Angstrom, V = 661.9 Angstrom(3) and Z = 4 form ula units per cell. The coordination sphere around the two crystallogr aphically different cerium atoms ore formed by seventeen and eighteen atoms. For rhodium and silicon atoms icosahedra and trigonal prisms wi th additional atoms are typical as coordination polyhedra. The structu re of Ce3Rh3Si2 is built up from CeRh2Si and Ce(Rh0.5Si0.5) slabs with YPd2Si and FeB-like atomic arrangement, respectively. The crystal che mistry of Ce3Rh3Si2 is compared with that of Ce3Rh2Ge2 with Y3Rh2Si2 t ype structure. (C) 1997 Elsevier Science S.A.