A partial substitution of phosphorus with the metal atom Co: the crystal structure of Hf5Co1+xP3−x

Abstract

Abstract The new phosphide Hf5Co1+xP3−x has been prepared by arc melting of HfP, Hf and Co, and subsequent annealing at 1500°C in an induction furnace. It crystallizes in a new structure type, space group Pnma (No. 62), lattice constants a = 16.980(3) A, b = 3.6101(7) A, c = 10.175(1) A, V = 623.8(2) A3. This structure consists of six-membered Hf-channels, condensed to a double channel. Each channel contains one Co and one P atom, which form an infinite CoP zigzag chain. The channels are connected via short HfHf contacts to a three-dimensional network with two further P positions located in trigonal prismatic voids of the Hf sublattice. Unusually, one P site — that with the higher bond order — is partially occupied with Co, indicating that phosphorus is able to take part in delocalized metallic bonds, as well as cobalt. The partial Co/P exchange is related to the similar atomic radii and the expected negative charge for Co and P in this Hf-rich phosphide. A significant phase range is observed.