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 arc melting of HfP and the corresponding 3 d metal, and subsequent annealing at 1400°C. The lattice constants vary from a = 6.247(2) Å, b = 3.7177(6) Å, c = 7.137(2) Å, V = 165.74(8) ų for HfFeP, a = 6.295(3) Å, b = 3.668(2) Å, c = 7.175(4) Å, V = 165.7(2) ų for HfCoP to a = 6.240(3) Å, b = 3.716(2) Å, c = 7.135(2) Å, V = 165.4(2) ų (HfNiP) in the orthorhombic space group Pnma. Although ZrNiP occurs only in the Ni₂In structure type, all three Hf phosphides crystallize in the Co₂Si structure type, isotypic to ZrFeP and ZrCoP. The structural differences between HfNiP and ZrNiP can be explained by the preference of Hf for structures with more metal-metal bonds rather than by size effects.