Nb_(28)Ni_(33.5)Sb_(12.5') a New Representative of the X-phase

摘要

The first ternary compound in the Nb-Ni-Sb system,Nb_(28)Ni(33.5)Sb_(12.5),has been synthesized and its structure has been determined by single-crystal X-ray diffraction methods.Nb_(28)Ni_(33.5)(2)Sb_(12.5)(2) adopts the X-phase structure type (oetho-rhombic,space group Pnnm,Z=1,a=13.2334(5)A,b=16.5065(7)A,c=5.0337(2)A),which belongs to the set of tet-rahedrally close-packed (TCP) structures adopted by many in-tetmetallic compounds.Typical of such TCP structures,the atoms reside in sites of high coordination number,with Ni and Sb in CN12 and Nb in CN14,-15,and -16 sites.The relative importance of various metal-metal bonding interactions is discussed on the basis of extended Huckel band structure calcu-lations.Nb_(28)Ni_(33.5)Sb_(12.5)displays metallic behavior with a room-temperature resistivity of 2.3X10~(-4) #OMEGA# cm.