Single Crystal X-Ray Diffraction Studies. Due to their air-sensitive character, the single crystals were selected, mounted on a glass fiber and sealed in a glass capillary inside an argon filled glove-box. Single-crystal X-ray diffraction data collection were done at ambient temperature (295 K) on an Oxford Diffraction Xcalibur3 diffractometer with CCD detector (Oxford Diffraction Ltd, UK), using graphite monochromatized Mo-Kα radiation (λ = 0.71073 Å), operated at 50 kV and 40 mA, and a detector-to-crystal distance of 60 mm. Full set of data were obtained by ω-scan with 0.5° rotation width and 15 sec exposure time per frame. Absorption correction, based on semi-empirical 'multi-scan' approach, was applied to the integrated reflections using the program CrysAlis RED. The space group space group C2/m (No 12), was indicated by the systematic absent reflections and confirmed by the successful structure solution (Shelxs-97) and refinement (Shelxl-97) using the SHELXTL software package. The assignment of Bi and Ba positions is straightforward using direct method. Then, five largest residual electron pics in the difference Fourier map were first assigned to In atoms, resulting in some large electron holes on three of these positions, which were subsequently refined as In/Zn mixed occupied positions. In fact, the refined In-contents in the crystal structures were found to increase as the Zn-content in the starting mixtures increase, seemingly due to competitive formation of ternary Ba2ZnBi2 phase in the products. Hence, the refined value of x = 0.21 was obtained from a starting mixture Ba5ZnnIn4-nBi5 with n = 1, while n = 2 yielded x = 0.47. As indicated in Table , best final refinement with secondary extinction correction yields satisfactory residuals for crystal with x = 0.21, R1 = 0.0483 and wR2 = 0.104 for observed and all reflections, respectively. The images are rendered using the program Diamond, version 2.1c. Most relevant crystallographic data and refinement details for the title compound Ba8Zn2-xIn3+xBi10 (for x = 0.21 and 0.47) are in summarized in Table and contains the atomic positions and equivalent displacement parameters. Local density approximation (LDA) was used to treat exchange and correlation according to Barth and Hedin. All relativistic effects except for spin-orbital coupling were considered by the scalar relativistic approximation. Since the crystal structure of Ba8In3+xZn2-xBi10 (x = 0.21-0.47) exhibits mixed occupied sites, an ordered model was used for calculations. In the model, the In4/Zn4 sites are fully occupied with In (exp.: 0.81In + 0.19Zn), whereas the Zn3/In3 and Zn5/In5 sites are fully occupied with Zn (exp.: 0.21In + 0.79Zn and 0.19In + 0.81Zn, respectively). Empty spheres (wave functions without nuclei) were introduced to improve packing and increase variational freedom. The position and radii of empty spheres were determined automatically by the program dedicated routine. Following basis sets were used: Ba, 6s(6p)5d4f; Bi, 6s6p(5d4f ); In, 5s5p(5d4f ); Zn, 4s4p3d; and empty spheres, 1s(2p) or 1s(2p3d). Partial waves in brackets were down-folded. Brillouin zone integrations were carried out using the tetrahedron method with 222 irreducible k-points.