Synthesis and structural characterization using the Rietveld method of the quaternary compound CuAlGeSe4

Sample of the quaternary phase CuAlGeSe4, a member of the I-III-IV--VI4 semiconductor system, was synthesized by the melt and annealing technique and analyzed using X-ray powder diffraction data. The indexing and refinement of the pattern indicate that this compound crystallizes in the tetragonal system, space group I (Nº82) with unit cell parameters: a = 5.5646(3) Å, c = 10.682(2) Å, V = 330.77(5) Å3. The space group was established from a cationic and anionic distribution analysis in the tetragonal space groups: I2d (Nº 122), I2m (Nº 121), and I (Nº 82), for an ordered structure in this material. The Rietveld refinement, performed with the starting model: Cu 2c, Al 2b, Ge 2d,  2a, and Se 8g, converged to Rexp= 7.2%, RP = 7.4%, Rwp = 9.6%, and χ2 = 1.7.