Synthesis, crystal structure, and electronic structure of Ba2GeTe3(Te2)

International audienceBlack crystals of Ba2GeTe3(Te2) were obtained by the "U-assisted" reaction of U, Ba, Ge, and Te at 1173 K using the sealed-tube method. The crystal structure of Ba2GeTe3(Te2) was determined by a single crystal X-ray study at 100(2) K. It crystallizes in space group Pnma of the orthorhombic crystal system with four formula units in a cell with constants a = 6.7900(14) Å, b = 23.720(5) Å, and c = 6.9300(14) Å. The crystal structure of Ba2GeTe3(Te2) can be described as pseudo one-dimensional with zigzag chains 1 ∞[GeTe3 2 ] where each Ge atom is bonded to four Te atoms in a distorted tetrahedron. These chains are separated by the Ba 2+ cations and homoatomic dimers of Te2 2. Around each Ba atom there are nine Te atoms in a distorted tricapped trigonal prism. Charge balance in Ba2GeTe3(Te2) is achieved with 2 × Ba 2+ , 1 × Ge 4+ , 3 × Te 2 , and 1 × Te2 2. Density functional theory (DFT) calculations suggest Ba2GeTe3(Te2) is a metal with Ge-and Te-derived states contributing the most around the Fermi level