Structural Analysis Of Fe2GeSe4, A II2 ( IV VI4 Semiconducting Compound. J.M. Delgado*, J.A. Henao*(1) and M. Quintero**. *Departamento de Química and ** Departamento de Física, Facultad de Ciencias, Universidad de Los Andes, Apdo Postal 40, La Hechicera, Mérida 5251, Venezuela.
Several structural studies have been reported for some members of the II2 (IV VI4 family of semiconducting compounds. These materials can be regarded as one of the four possible families of fourfold defect derivatives of the II VI binaries in which the cation has been substituted by two or three types of cations and an array of vacancies is introduced (the other families are II _ III2 VI4, I III IV _ VI4 and I II V _ VI4).
The structural studies carried out on some members of this family of materials indicate that they crystallize in three basic groups of structures: A distorted spinel structure with the tetragonal space group I41/a (No. 88), reported initially for Fe2SnS4, an olivine-type of structure (olivine: Mg2SiO4, space group Pnma (No. 62)) and a structure type with the orthorhombic space group Cmmm (No. 65) reported for Mn2SnS4.
In this contribution, a structural analysis of Fe2GeSe4, carried out using the Rietveld method, is presented. To our knowledge, there are no reports in the literature of studies performed on this material. Fe2GeSe4 was found to be orthorhombic, a = 13.069(1), b = 7.559(1), c = 6.2037(6) Å, V = 612.83(9) Å3, Z = 4, Dx = 5.42 g.cm-3. The structure refinement carried out using the Rietveld method indicated that this material crystallizes in space group Pnma (No. 62) with an olivine type of structure. The refinement of 33 parameters led to RWP = 15.3%, RP = 10.2% for 5251 step intensities and RB = 9.44% and RF = 9.36% for 913 reflections.
(1)Permanent address: Escuela de Química, Facultad de Ciencias, Universidad Industrial de Santander, Apdo Aéreo 678, Bucaramanga, Colombia.
Acknowledgement is made to the Programa de Nuevas Tecnologías of CONICIT, through grant NM-18 and to CDCHT-ULA for grant C-727-95-08-A.