Novel Quaternary Metal-Rich Phosphides:  Stabilization by Differential Fractional Site Occupancies and Polar Intermetallic Bonding

Abstract

The new phosphide Hf5Nb5Ni3P5 has been prepared by arc-melting of a pressed stoichiometric mixture of HfP, Nb, and Ni. Single crystals suitable for the structure determination were obtained after annealing in an induction furnace at 1350 °C. Hf5Nb5Ni3P5 crystallizes in the hexagonal space group P6̄2m (No. 189). The early transition metal atoms Hf and Nb are found on three crystallographically different sites, with refined occupancies of 100% Hf for the M1, 59.5(4)% Hf and 40.5(4)% Nb for the M2, and 13.1(6)% Hf and 86.9(6)% Nb for the M3 site. Small variations of the Hf to Nb ratio are possible, occurring with significantly different lattice parameters. The early transition elements form a three-dimensional framework with numerous M−M (M = Hf, Nb) interactions, including Ni and P in its trigonal prismatic voids. The differential fractional site occupancies can be understood on the basis of the different preferences of Hf and Nb to form M−M, M−Ni, and M−P bonds. The metallic character is confirmed by the Pauli paramagnetism experimentally obtained.

Structur–Composition Relations and Fractional Site Occupancy of New M5Ge4 Compounds in the System Ge–Ta–Zr

“…Phase transitions into closely related neighboring phases, such as in the Ge}Ta}Zr system, are only triggered if the range of continuous variation within a single structure is exceeded. As DFSO-stabilized phases with noticeable composition ranges have also been reported in other systems (23,24), it may in fact be assumed that this more general DFSO mechanism is quite common among mixed early transition metal compounds. The application of this generalized DFSO concept may be a valuable tool, not only for the prediction of new ternary and multinary compounds in similar systems, but also for the estimation of site preferences based upon calculated Mulliken overlap population in systems, where such data are not readily available.…”

Ternary borides Nb7Fe3B8 and Ta7Fe3B8 with Kagome-type iron framework

“…Later another ordering variant for this atomic motif was discovered in Hf 5 Nb 5 Ni 3 P 5 : Hf 1 (Hf,Nb) 6 (Hf,Nb) 3 P 2 (Ni,P) 6 . 65 The structural motif of TM 7 Fe 3 B 8 can be described as a 2D intergrowth of the (Fig. 4b), this atomic pattern plays important role in the magnetic behavior of these materials (cf.…”

Nb28Ni33.5Sb12.5, a New Representative of the X-phase

“…The atomic parameters used (3,33) are listed in Table 5. Properties were extracted from the band structure using 45 k-points in the irreducible portion of the Brillouin zone.…”