Crystal Structure and Physical Properties of the New One-Dimensional Metal Ba₂Cu_7–<i>x</i>Te₆

Abstract

The telluride Ba₂Cu_7–<i>x</i>Te₆ was synthesized from the elements in stoichiometric ratios, heated to 1073 K, followed by slow cooling to 873 K over 120 h. Ba₂Cu_7–<i>x</i>Te₆ crystallizes in space group <i>P</i>2₁/<i>m</i> with lattice dimensions of <i>a</i> = 6.8591(7) Å, <i>b</i> = 12.1439(12) Å, <i>c</i> = 9.0198(9) Å, β = 110.7509(14)°, <i>V</i> = 702.58(12) ų, and <i>Z</i> = 2. The structure is comprised of Cu atoms forming a six-membered ring and triangles, interconnected to an infinite ribbon of Cu atoms. The ribbons are connected to each other via Cu–Te bonds to yield a three-dimensional structure, wherein each Cu atom is tetrahedrally coordinated by four Te atoms. A special feature of this telluride is the occurrence of a quasi-linear Te atom chain, which causes one-dimensional metallic properties, in accordance with electronic structure calculations and property measurements