Glass relaxation and hysteresis of the glass transition by molecular dynamics simulations

Abstract

As out-of-equilibrium materials, glasses continually tend to relax toward the metastable supercooled liquid state. Glass relaxation can result in a non-reversible glass transition upon a cooling/reheating cycle. Here, based on molecular dynamics simulations, we present a novel methodology combining thermal cycles and inherent configuration analysis to investigate the features of relaxation and glass transition reversibility. By considering three archetypical silicate glasses, viz., silica, sodium silicate, and calcium aluminosilicate, we show that, for all the glasses considered herein, the enthalpy relaxation can be well described by mode-coupling theory. Further, we demonstrate the existence of a decoupling between enthalpy and volume relaxation. Finally, we show that enthalpy relaxation results in a non-reversible glass transition-the degree of non-reversibility being strongly system-specific.

New insights into the structure of sodium silicate glasses by force-enhanced atomic refinement

“…6c, the glass density predicted by MQ-MD simulations expectedly tends to increase upon decreasing cooling rate. This echoes the fact that glasses usually become more compact upon slower cooling rate (with the notable exception of pure silica) [14,50]. However, as the cooling rate decreases, we note that MQ-MD simulations tend to overestimate the density of sodium silicate observed experimentally, i.e., 2.45 g/cm 3 [44,51].…”

Predicting Composition-Structure Relations in Alkali Borosilicate Glasses Using Statistical Mechanics

“…To correct for the thermal history difference, the T f values for the MD simulated glasses have been determined by extrapolating experimental data (Grandjean et al, 2008) the same way as shown in Figure 2A, i.e., all T f values have been scaled with a constant relative to the experimental values. The predicted T f values by this method are generally in good agreement with those determined by using the method of Liu et al (2018) (see Figure S5).…”

“…Fictive temperatures (T f ) were found by employing the method of Liu et al (2018). This method uses local groundstate enthalpy as a function of temperature to estimate T f , giving very well-defined transitions compared to common methods of temperature-enthalpy plots as the method only considers the enthalpy of the atomic configuration at each temperature, leaving out contributions of atom dynamics.…”

Atomic Structure and Modifiers Clustering in Silicate glasses: Effect of Modifier Cations

“…In order get some insights into the atomic structure of the glass, we use molecular dynamics (MD) simulations, which is an effective method to help to investigate and understand the atomic-scale behavior of materials and have been applied in studying and oxide glasses [6,7,[34][35][36]. We study the effect of the modifier type on the structural properties of a series of modified silicate glasses were the concentration of the modifiers was fixed to 25 mol%.…”