STRUCTURE OF ORTHORHOMBIC YNIAL3

Nickel yttrium trialuminide, M(r) = 228.56, orthorhombic, new type, omicron-P20, Pnma - c5 (No. 62), a = 8.156 (1), b = 4.0462 (4), c = 10.638 (2) angstrom, V = 351.06 (6) angstrom 3, Z = 4, D(x) = 4.324 Mg m-3, lambda(Mo K-alpha) = 0.71073 angstrom, mu = 22.826 mm-1, F(000) = 424, T = 293 K, wR = 0.057 for 362 contributing unique reflections. The coordination numbers are Y 19, Ni 9 and Al 12. The YNiAl3 structure is related to YNiAl2 with an MgCuAl2-type structure and YNiAl4 with its own type. In all three structures the Y atoms are at the centres of pentacapped pentagonal prisms, the Ni atoms are at the centres of tricapped trigonal prisms of composition Y2Al4 and the Al atoms are at the centres of deformed cubes with four additional neighbours.