Synthesis and Structure of a Nonstoichiometric Zr 3.55 Pt 4 Sb 4 Compound

A nonstoichiometric ternary antimonide, Zr3.55Pt4Sb4, with a new structure type (hP24), has been synthesized via arc-melting. Its crystal structure was determined by single-crystal X-ray diffraction with hexagonal space group P63/mmc and lattice parameters a = 4.391(3) A, c = 30.53(2) A, and V = 509.7(8) A3. It features the unique Pt4Sb4 slab with Pt–Pt bonds and is reminiscent to hexagonal diamond substructures. Three different Zr atoms, occupying three different sites, aid in the close-packing of the Pt and Sb atoms. Electronic structure calculations show the half occupancy of one Zr site creates a pseudogap at the Fermi level and optimizes the Pt–Sb bonding interactions. This enhances the electronic stability and accounts for the very narrow phase width observed for this nonstoichiometric compound. Furthermore, strong Zr–Pt and Zr–Sb interactions play a crucial role in the chemical bonding of the title compound. Electrical transport measurements show metallic behavior of this compound down to 2 K, cons...