Sc9Te2:: A two-dimensional distortion wave in the scandium-richest telluride

Sc9Te2 was prepared by high-temperature solid-state techniques, and the structure was determined by single-crystal X-ray diffraction to be monoclinic, Cc (No. 9, Z = 8) with a = 7.7576(1) Angstrom, b = 15.654(3) Angstrom, c = 17.283(3) Angstrom, and beta = 90.01(3)degrees at 23 degrees C. The structure of metallic Sc9Te2 can be viewed as columns built either from distorted 3 x 3 bcc metal atoms or from distorted edge-sharing octahedra along (a) over bar that are joined via intercolumn bonds on opposite sides into two-dimensional layers along (b) over bar. A corrugated layer of Te atoms separates the metal layers in the c direction. This structure derives from the Ti9Se2 structure, with doubled a and b dimensions and a lower symmetry. Magnetic susceptibility measurements on Sc9Te2 show a substantially temperature-independent paramagnetism that is much smaller per metal atom than those for other scandium-rich tellurides or scandium metal. Extended Huckel band calculations reveal a clear distinction between high overlap populations for Sc-Sc interactions in the interior of the condensed metal structure and lower values for those on the exterior that have Te neighbors. The distortion generally enhances the overlap populations of occupied states.