Density-driven defect-mediated network collapse of <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi mathvariant="normal">GeSe</mi><mn>2</mn></msub></math></span> glass

International audienceThe 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 neutrondiffraction work at pressures8.2 GPa employed themethod of isotope substitution, and the molecular dynamicssimulations 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 transformationsthat differ substantially from those observed in common oxide glasses such as SiO2 and GeO2. Edge-sharingtetrahedra persist as important structural motifs until a threshold pressure of∼8.5GPa is attained,whereupon amediatingrole is found for homopolar bonds in the appearance of higher coordinated Ge-centered polyhedra. Thesemechanisms of network transformation are likely to be generic for the class of glass-forming materials wherehomopolar bonds and fragility-promoting edge-sharing motifs are prevalent in the ambient-pressure networ