Crystal structure of HT-Ni5P2 and reinvestigation of isotypic Ni5As2

The crystal structure of Ni5As2 is reinvestigated, and the synthesis and determination of the crystal structure of the HT-Ni5P2 using single crystal X-ray data are described. Ni5As2 crystallizes in space group P63cm, Pearson symbol hP48, a = 0.68253(1) nm, c = 1.25197(4) nm, V = 0.5051(1) nm3, Z = 6, RF = 0.041, wRF = 0.042 for 1196 independent reflections with F(hkl) > 4σF(hkl). The high temperature modification of the binary phosphide HT-Ni5P2 is isotypic with the arsenide, a = 0.65795(7) nm, c = 1.2261(5) nm, V = 0.4597(2) nm3, Z = 6, RF = 0.058, wRF = 0.135 for 504 independent reflections with F(hkl) > 4σF(hkl). The structure types of Ni5As2 and earlier known LT-Ni5P2 are closely related, and can be described as distorted variants of the Pd5Sb2 structure.