Crystal Structure Of The New Silicide Lani11.8-11.4si1.2-1.6

The intermetallic compound LaNi(11.8-11.4)Si(1.2-1.6 )was synthesized by arc-melting and its crystal structure was determined using powder and single-crystal X-ray diffraction data. The compound adopts the cubic CaCu6.5Al6.5-type structure (space group Fm (3) over barc, Pearson code cF112, Z = 8), which is a partially ordered ternary derivative of the NaZn13 type: alpha = 11.256(4) angstrom, V = 1426.1(15) angstrom(3), R = 0.0133, wR = 0.0285 for 93 reflections with I > 2 sigma(I) for LaNi11.4Si1.6; a = 11.25486(8) angstrom, V = 1425.68(2) angstrom(3) , R-p = 4.17%, R-wp = 5.85%, R-B = 3.44% for LaNi11.8Si1.2. One of its crystallographic positions (96i) is occupied by a mixture of Ni and Si atoms. The structure of this new silicide can be represented as a packing of Ni-centered icosahedra and La-centered snub cubes, which are packed in a CsCl-related manner.