STRUCTURE, CHEMICAL BONDING, AND PROPERTIES OF SC2NI2IN

Sc2Ni2In was prepared by a reaction of the elemental components in an are furnace and subsequent annealing at 1070 K. Sc2Ni2In is a Pauli pa ramagnet and a poor metallic conductor with a specific resistivity of 224 m Omega cm at room temperature. Its crystal structure was refined from X-ray powder data: P4/mbm, a = 716.79(1) pm, c = 333.154(8) pm, Z = 2, R(wp) = 0.040, and R(B)(I)= 0.026. Sc2Ni2In crystallizes with a ternary ordered version of the U3Si2-type structure. The nickel and in dium atoms occupy [NiSc6] trigonal prisms and [InSc8] square prisms, r espectively. These structural fragments are derived from the AlB2 and CsCl-type structures. Semi-empirical band structure calculations revea l Sc2Ni2In to be a nickelide, and the strongest bonding interactions a re found for the Sc-Ni contacts, followed by Sc-In and Ni-In. A rigid- band model suggests the existence of the isotypic phase Sc2Ni2Sb.