Two-Gaussian excitations model for the glass transition

Abstract

We develop a modified "two-state" model with Gaussian widths for the site energies of both ground and excited states, consistent with expectations for a disordered system. The thermodynamic properties of the system are analyzed in configuration space and found to bridge the gap between simple two state models ("logarithmic" model in configuration space) and the random energy model ("Gaussian" model in configuration space). The Kauzmann singularity given by the random energy model remains for very fragile liquids but is suppressed or eliminated for stronger liquids. The sharp form of constant volume heat capacity found by recent simulations for binary mixed Lennard Jones and soft sphere systems is reproduced by the model, as is the excess entropy and heat capacity of a variety of laboratory systems, strong and fragile. The ideal glass in all cases has a narrow Gaussian, almost invariant among molecular and atomic glassformers, while the excited state Gaussian depends on the system and its width plays a role in the thermodynamic fragility. The model predicts the existence of first-order phase transition for fragile liquids.

12 pages, 12 figures

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Cited by in corpus (8)

• Tuning of tetrahedrality in a silicon potential yields a series of monatomic (metal-like) glassformers of very high fragility
• Gaussian excitations model for glass-former dynamics and thermodynamics
• Properties of ideal Gaussian glass-forming systems
• Normal modes, and acoustic properties, of an elastic solid with line defects
• Model Energy Landscapes of Low-Temperature Fluids: Dipolar Hard Spheres
• "Fragile superconductivity": a kinetic glass transition in the vortex matter of the high-temperature superconductor YBa2Cu3O7-d
• Discovery of a paired Gaussian and long-tailed distribution of potential energies in nanoglasses
• Thermodynamics and Dynamics of a Monoatomic Glass-Former. Constant Pressure and Constant Volume Behavior