Unique Periodic Modulations in the Infinite [Tex]n−Chains of RbUSb0.33Te6

Abstract

The new phase RbUSb0.33Te6 is described. The structure of RbUSb0.33Te6 is acentric and trigonal (space group P3) with infinite [UTe6]2− columns running along the c axis. The structure has straight [UTe6]6− columns in which the U atoms adopt distorted tri-capped trigonal prisms. The central axis in the [UTe6]2− columns is defined by a row of U atoms 4.064 (1) Å apart, i.e., a metal “wire” seethed with what appear to be three infinite zig-zag Te chains. The crystals, however, exhibit a superstructure that results in a rhombohedral space group which is 9 times larger (asuper=3asub, bsuper=3bsub, csuper=3csub) than that of the ideal P3 structure. The superstructure is caused by a periodic modulation of Te–Te distances in the zig-zag chains. The almost equal Te–Te distances in the infinite chains are in fact dimers, trimers, and pentamers. The material is a narrow gap semiconductor with a room temperature electrical conductivity of ∼40 S/cm.