SYNTHESIS, CRYSTAL-STRUCTURE, AND PROPERTIES OF HFM'P (M'=FE, CO, NI)IN COMPARISON TO ZRNIP

The new phosphides HfM'P (M' = Fe, Co, Ni) have been synthesized by ar e melting of HfP and the corresponding 3 d metal, and subsequent annea ling at 1400 degrees C. The lattice constants vary from a = 6.247(2)An gstrom, b = 3.7177(6)Angstrom, c = 7.137(2) Angstrom, V = 165.74(8) An gstrom(3) for HfFeP, a = 6.295(3) Angstrom, b = 3.668(2) Angstrom, c = 7.175(4) Angstrom, V = 165.7(2) Angstrom(3) for HfCoP to a = 6.240(3) Angstrom, b = 3.716(2) Angstrom, c = 7.135(2) A, V = 165.4(2) Angstro m(3) (HfNiP) in the orthorhombic space group Pnma. Although ZrNiP occu rs only in the Ni2In structure type, all three I-If phosphides crystal lize in the Co2Si structure type, isotypic to ZrFeP and ZrCoP. The str uctural differences between HfNiP and ZrNiP can be explained by the pr eference of Hf for structures with more metal-metal bonds rather than by size effects.