title: Linking rigidity transitions with enthalpic changes at the glass transition and fragility: insight from a simple oscillator model.
abstract: A low temperature Monte Carlo dynamics of a Keating-like oscillator model is used to study the relationship between the nature of network glasses from the viewpoint of rigidity, the thermal reversibility during the glass transition and the strong-fragile behaviour of glass-forming liquids. The model shows that a Phillips optimal glass formation with minimal enthalpic changes is obtained under a cooling/annealing cycle when the system is optimally constrained by the harmonic interactions, i.e. when it is isostatically rigid. For these peculiar systems with a nearly reversible glass transition, the computed activation energy for relaxation time shows also a minimum, which demonstrates that isostatically rigid glasses are strong (Arrhenius-like) glass-forming liquids. Experiments on chalcogenide and oxide glass-forming liquids are discussed under this new perspective and confirm the theoretical prediction for chalcogenide network glasses whereas limitations of the approach appear for weakly interacting (non-covalent, ionic) systems.
authors.affiliation: Laboratoire de Physique Théorique de la Matière Condensée, UPMC-Université Paris 6, CNRS UMR 7600, Boite 121, 4 place Jussieu, F-75252 Paris Cedex 05, France.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Micoulaut
mesh_terms: D003080:Cold Temperature; D003198:Computer Simulation; D004735:Energy Transfer; D005898:Glass / Q000737:chemistry*; D008956:Models, Chemical; D009991:Oscillometry / Q000379:methods*; D044367:Phase Transition