Density-driven defect-mediated network collapse of GeSe2 glass

Kamil Wezka, Assil Bouzid, Keiron J. Pizzey, Philip S. Salmon, Anita Zeidler, Stefan Klotz, Henry E. Fischer, Craig L. Bull, Matthew G. Tucker, Mauro Boero, Sébastien Le Roux, Christine Tugène, Carlo Massobrio

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Abstract

The evolution in structure of the prototypical network-forming glass GeSe2 is investigated at pressures up to ∼16 GPa by using a combination of neutron diffraction and first-principles molecular dynamics. The neutron diffraction work at pressures ≤8.2 GPa employed the method of isotope substitution, and the molecular dynamics simulations were performed with two different exchange-correlation functionals, the Becke-Lee-Yang-Parr (BLYP) and the hybrid Heyd-Scuseria-Ernzerhof HSE06. The results show density-driven structural transformations that differ substantially from those observed in common oxide glasses such as SiO2 and GeO2. Edge-sharing tetrahedra persist as important structural motifs until a threshold pressure of ∼8.5 GPa is attained, whereupon a mediating role is found for homopolar bonds in the appearance of higher coordinated Ge-centered polyhedra. These mechanisms of network transformation are likely to be generic for the class of glass-forming materials where homopolar bonds and fragility-promoting edge-sharing motifs are prevalent in the ambient-pressure network.

Original languageEnglish
Article number054206
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume90
Issue number5
DOIs
StatePublished - Aug 26 2014
Externally publishedYes

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