The synthesis, structure, and band structure analysis of the quaternary compound Ko.33Bao.6?AgTe2 are reported. Crystals of Ko.33Bao.67AgTe2 were obtained in a K2Te/BaTe/Te flux by the reaction of 1 mmol of K2Te, 0.5 mmol of BaTe, 0.5 mmol of Ag, and 4 mmol of Te in an evacuated Pyrex tube at 450 °C for 3 days followed by a slow cooling to 150 °C. The compound has a substructure in the tetragonal space group IMmmm (no. 139) with flsub = 4.624(2) A, csub = 23.326(4) A, V = 498.7(3) A3, at 20 °C (Mo Ka radiation): Z = 4, Dcalc = 6.23 g/cm3, 20max = 50°, data collected: 592, independent data: 172, observed with / > 3o(I): 108, variables: 13, final R = 0.054, Ry, = 0.067. Ko.33Bao.67AgTe2 has a lamellar structure related to that of Nai.9Cu2Se2*Cu20. The substructure contains a readily recognizable [Te2]4/3_ square net. The closest Te-Te distance in the net is 3.269(2) A, not a full covalent bond, but too short for a simple van der Waals contact. While it is predicted that the square [Te2]4/3_ net has metallic properties, the experimental data show a semiconductor behavior which has its origins in a structural distortion. Electron diffraction measurements reveal the presence of two different but related superstructures; an incommensurate orthorhombic superstructure of the tetragonal cell with asuper = 2.84asub, bsuper = bSUb, and csuper = cSub, and a commensurate tetragonal superstructure with asuper = 3asub, bsuper = 3bsub, and csuper = cSUb. Both extended-Hiickel and Hiickel calculations suggest that this distortion is a charge density wave. In the case of the incommensurate cell, the theoretically predicted supercell corresponds to the experimentally observed. We also used the /^-scaled Hiickel method to predict the actual atomic positions within the supercell. The theoretically predicted superstructures have calculated diffraction patterns similar to the experimentally observed ones.Here, we describe the synthesis, electronic structure studies, and
