Résumé
Single crystals of Pt2Ga17Ta3 were flux-grown in a high-temperature experiment from a Pt-Ga mixture heated in a sealed tantalum crucible. Typical crystals of this intermetallic compound are hexagonal platelets. The stoichiometry of the compound has been confirmed by energy-dispersive X-ray spectrometry (EDS) and its structure is determined by single-crystal X-ray diffraction at room temperature. Pt2Ga17Ta3 crystallizes in a new structural type, with hexagonal symmetry P63/mmc and unit cell of dimensions a = 8.1930(4), c = 13.6151(6) Å. The structure is described as a packing of polyhedral units, triangular prisms Pt@Ga6 and complex units Ta3@Ga20 built from three interpenetrating Ta@Ga10Ta2 distorted icosahedra. The compound properties are evaluated from DFT first-principle calculations against those of the In- and Nb- isostructural analogs Pt2X17M3, X = Ga, In, M = Ta, Nb. Results indicate that these compounds are likely to be stable and exhibit similar behavior to Pt2Ga17Ta3, a compound where binding occurs primarily through metallic interactions despite the presence of localized covalent bonds.