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The Cu 2 GeTe 3 compound crystallizes in the Imm2 (N° 44) space group, Z = 2, with a = 12.641(1) Å, b = 4.2115(2) Å, c = 5.9261(2) Å, V = 315.49(3) Å 3 . Its structure was refined from X-ray powder diffraction data using the Rietveld method. The refinement of 23 instrumental and structural variables led to R p = 8.2%, R wp = 11.6%, R exp = 6.8%, R B = 11.2 % and S = 1.7, for 5501 step intensities and 253 independent reflections. This compound is isostructural with Cu 2 GeSe 3 , and consists of a three-dimensional arrangement of slightly distorted CuTe 4 and GeTe 4 tetrahedra connected by common corners.

The crystal structure of the adamantane compound CuFeInSe3, belonging to the system (CuInSe2)1–x (FeSe)x with x = 0.5, was analyzed using X‐ray powder diffraction data. Several model structures were derived from the structure of the selenium rich phase CuInSe2.3 by permuting the cations in the available Wyckoff positions. The refinement of the best model by the Rietveld method in the tetragonal space group P$ \bar 4 $2c (Nº 112), Z = 1, with unit cell parameters a = 5.7762(2) Å, c = 11.5982(7) Å and V = 386.97(3) Å3 led to Rp = 8.0%, Rwp = 9.6%, Rexp = 6.2% and χ2 = 1.7 for 134 independent reflections. The model that best fitted the diffraction data has the following atomic distribution: Cu in Wyckoff site 2f; Fe in Wyckoff site 2d; In in Wyckoff site 2b and 1/3Cu, 1/3Fe, 1/3In in Wyckoff site 2f; Se in Wyckoff site 8n. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

X-ray powder diffraction study of the p-type semiconductor Cu2SnSe4 shows that this material crystallizes in the cubic structure, space group F4¯3m, with unit cell parameter a=5.6846(3) Å. The temperature variation of the hole concentration between 120 and 300 K, obtained from the Hall effect and electrical resistivity measurements, is due to the thermal activation of an acceptor level with ionization energy of about 0.02 eV. The temperature variation of the hole mobility is explained by considering the scattering of charge carriers by ionized impurities and acoustic phonons. From this analysis, the density-of-states effective mass of the holes is estimated to be about 0.8 me, me being the free electron effective mass. From the optical absorption spectra, the fundamental absorption edge is found to be direct. The value of the lowest energy gap and the spin-orbit splitting were estimated to be about 0.35 and 0.20 eV, respectively. The temperature dependence of the magnetization measurements shows that Cu2SnSe4 is paramagnetic, indicating that most of the copper atoms have the divalent charge state.

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