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Topological Phases of Chalcogenide Glasses Encoded in the Melt Dynamics

2018; Wiley; Volume: 255; Issue: 6 Linguagem: Inglês

10.1002/pssb.201800027

1521-3951

P. Boolchand, Mathieu Bauchy, M. Micoulaut, Can Yildirim,

Glass properties and applications

Select Raman scattering and modulated differential scanning calorimetry (DSC) experiments on specially homogenized binary Ge x Se 100– x and Ge x S 100– x chalcogenide glasses, supported by ab initio MD simulations are undertaken. In both chalcogenides, the glasses exhibit a super‐strong behavior (with a melt fragility index, m ( x ) < 20) in the 20(1)% < x < 26(1)% composition range, defining the fragility window, and with m ( x ) > 20 as one goes away from the fragility window. Remarkably, molecular dynamics (MD) simulations confirm the existence of the fragility window. Furthermore, in both chalcogenide glasses, the enthalpy of relaxation at T g , Δ H nr ( x ), becomes minuscule (≈0) in the 20(1)% < x < 26(1)% range, defining the reversibility window, and with Δ H nr ( x ) increasing by an order magnitude abruptly with x outside that window. Thus, super‐strong melts formed in the fragility window give rise to isostatically rigid glasses in the reversibility window and fragile melts formed at x < 20(1)% and at x > 26(1)% give rise to flexible‐ and stressed‐rigid glasses, respectively. Melt dynamics for the examined glass systems unequivocally encode the nature of the glass topological phases.