A NEW PHASE IN THE TL-AG-TE SYSTEM - CRYSTAL-STRUCTURE OF TL4AG18TE11

A new stable phase in the ternary Tl-Ag-Te system has been identified. X-ray diffraction examination of single crystals was used to establish the crystal structure of Tl4Ag18Te11. The cubic space group is F43mBAR and the lattice parameter is a = 1.8717(8) nm, Z = 8. The relationship to the cubic BaHg11-type structure and the In2Te3-type structure are established. The structure is described as a three-dimensional array of large channels of silver and tellurium atoms hosting linear chains of thallium atoms. These independent channels are built up with cubes and square antiprisms stacked along the fourfold axis and they are connected by smaller channels built up with smaller square antiprisms and cubes hosting tellurium atoms.