Defects in a disordered world: the structure of glassy GeSe2

Area of Science:

• Materials Science
• Solid State Chemistry
• Neutron Scattering

Background:

• Germanium diselenide (GeSe2) is a prototypical network glass with potential applications in various fields.
• Understanding the local atomic structure and chemical bonding is crucial for predicting material properties.
• Previous studies have provided insights, but a comprehensive analysis of partial structure factors is needed.

Purpose of the Study:

• To precisely determine the partial structure factors of GeSe2 glass using isotopic substitution.
• To investigate the prevalence of edge-sharing and corner-sharing Ge(Se1/2)4 tetrahedra.
• To quantify the extent of homopolar Ge-Ge and Se-Se bonds in the glass network.

Main Methods:

• Neutron diffraction experiments were performed on isotopically substituted GeSe2 samples.
• Isotopic substitution enabled the separation of partial structure factors.
• Data analysis involved Rietveld refinement and pair distribution function (PDF) analysis.

Main Results:

• The study successfully measured the full set of partial structure factors for GeSe2 glass.
• It was found that 34(5)% of Ge atoms are in edge-sharing configurations within Ge(Se1/2)4 tetrahedra.
• A significant fraction of homopolar bonds was observed: 25(5)% Ge-Ge and 20(5)% Se-Se, indicating chemical disorder.

Conclusions:

• The research provides a detailed atomic-level understanding of the structure of GeSe2 glass.
• The presence of homopolar bonds highlights deviations from ideal chemical ordering.
• These findings are essential for the development and application of chalcogenide glasses.