Ternary phosphide Ho2Cu6-xP5-y, its crystal structure, and REm+n(Cu2P3)(m)(Cu4P2)(n) relationship with other rhombohedral rare-earth copper phosphides

摘要

Crystals of the phosphide Ho2Cu6-xP5-y (x = 0.41, y = 0.50) have been prepared by annealing pressed powders of the elements at 800 degrees C for 2 weeks. The structure was determined by single-crystal methods: space group R(3) over bar m (No. 166), Z = 3, a = 3.976(1) Angstrom, c = 40.554(8) Angstrom, R = 0.045 for 243 independent reflections [F> 4 sigma(F)]. The unit cell of Ho2Cu6-xP5-y can be built from a close packing of Ho atoms and fragments of Cu3P, with one of the fragments containing additional P atoms, It can be also considered as an intercalation of additional P atoms in the YbCu3-xP2 structure (P. Klufers, A. Mewis, and H. U. Schuster, Z. Kristallogr. 149, 211 (1979)). The REm+n(Cu2P3)(m)(Cu4P2)(n) relationship with other rare-earth copper phosphides, having similar structural characteristics is discussed. (C) 2000 Academic Press. [References: 16]