Abstract

High-resolution 77Se MAS NMR spectroscopy has been conducted at 11.7 T to investigate the short-and intermediate- range structure and chemical order in binary GexSe100−x glasses with 5 ≤ x ≤ 33.33. Four distinct Se environments are observed for the first time, corresponding to Se−Se−Se and Ge−Se−Se linkages as well as Ge−Se−Ge sites where the Se atom is shared by two GeSe4 tetrahedra in either corner-sharing or edge-sharing configuration. Assignments of corner and edge-shared tetrahedra were made based on the 77Se MAS NMR spectrum of crystalline β-GeSe2. Analysis of the compositional variation of the relative concentrations of these Se sites indicates that the structure of GexSe100−x glasses in this composition range can be described as a randomly interconnected network of GeSe4 tetrahedra and chains of Se atoms. The implications of this structural model are discussed in relation to the composition dependence of the glass-forming ability and kinetic fragility of the corresponding parent liquids.

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