Crystal and Electronic Structure of a Quaternary Layered Compound from the K–In–Ge–Sb System: K9In9GeSb22

Abstract

The quaternary Zintl phase material, K9In9GeSb22(1), has been prepared at 650°C and its structure determined by single crystal X-ray diffraction: triclinic, space groupP1witha= 11.62 (1) Å,b= 13.04 (3) Å,c= 11.27 (2) Å, α = 113.5 (2)°, β = 91.7 (1)°, γ = 112.3 (1)°,V= 1415 (4) Å3, andDcalcd= 4.851 g/cm3forZ= 2 andR(Rw) = 7.9% (8.8%). Antimonide 1 contains layers comprised of indium, germanium, and arsenic separated by K+cations. The In–Ge–Sb layers in 1 contain In(2−x)GexSb6(x≅ 1) dimers with In(Ge)–In(Ge) bonds, InSb4tetrahedra, and Sb3trimers, as well as infinite chains with Sb–Sb bonds. There is an unusual metal–metal bonded site in 1, that contains contains a solid solution of 1:1 In and Ge, with an In(Ge)–In(Ge) separation of 2.659 (1) Å. The nature of this experimentally determined solid solution at theM–Mbonded site, and its effects on the electronic structure of K9In9GeSb22, was investigated via tight binding calculations.