Glass formation and properties of chalcogenide systems XXXII. RDF studies on the structure of vitreous Ge 2S 3 and Ge 2Se 3

Abstract

X-ray diffraction measurements and RDF calculations are reported for the bulk glasses Ge 2S 3 and Ge 2Se 3 as well as for amorphous precipitated Ge 2Se 3 supported by pair function calculations based on a model for Ge 2S 3 constructed by hand taking into consideration a GeGe bond length of 244 pm and GeS distances of 219–223 pm. Because of the comparatively sufficient accordance between the model RDF and the experimental RDF up to the third peak and with regard to the peak positions even up to the fith maximum the Ge 2S 3 glass structure can be approached by a three-dimensionally connected network of Ge 2S 6/2 units which are predominantly corner-shared: GeSGe angle distribution 95–145° with a maximum at 120°. The small differences between the RDF of vitreous GeS 2 and Ge 2S 3 which consist of different units revealed by the peak areas of the first and third peak and especially by the unsplit fourth maximum for glassy Ge 2S 3 suggest precaution in the structural interpretation of RDFs. The RDFs of the two differently prepared amorphous Ge 2Se 3 samples are widely in accordance; however, the RDF of vitreous GeSe 2 as well, except the unsplit fourth peak for Ge 2Se 3 which is more resolved than in the RDF of Ge 2S 3.