Crystal and electronic structures of the new ternary gallide Zr12Pd40−xGa31+y (x = 0–1.5, y = 0–0.5)

Abstract

Zr12Pd40Ga31 was prepared from the elements by arc melting under argon and subsequent annealing at 870 K for 720 h. Single-crystal X-ray diffraction reveals that Zr12Pd40Ga31 crystallizes in a new hexagonal structure type: Pearson symbol (PS) hP166, space group P6/mmm, a = 18.7670(6) Ǻ, c = 8.6634(6) Ǻ). The crystal structure consists of three types of atomic layers – two flat sheets at z = 0 (layer A) and z = 0.5 (C) and one corrugated at z = 0.25 and z = 0.75 (B), which stack in the sequence … ABCB … along the [001] direction. The structure shows close vicinity to a series of hexagonal structures with PS hP164–hP171. These compounds show peculiar structural variability expressed in the different atomic occupations of the Wyckoff positions along and around the 3-fold and 6-fold axes. Homogeneity range and lattice parameters of new ternary compound Zr12Pd40−xGa31+y (x = 0–1.5, y = 0–0.5) have been refined from EDX and powder XRD data. Electronic structure calculations and bonding analysis have been performed for an idealized model revealing domination of the Pd–Ga and Ga–Ga interactions.