Thermometer Effect: Origin of the Mixed Alkali Effect in Glass Relaxation

Crystals at High Deformation Rates Displaying Glassy Behavior

“…In fact, such a model fails to describe correctly the behavior at short and intermediate times. Here, the decay of the corresponding relaxation function is found to be more accurately fitted with a Kohlrausch–Williams–Watts (KWW) profile of the form , and this can be fully evidenced from an appropriate plot used in this kind of studies (Figure b) which represents with as a function of log( t ) and leads to a straight line for the stress relaxation, the slope being equal to the stretching exponent β of the KWW form. Interestingly, β also exhibits the threshold‐like behavior (Figure c), previously noticed for E and σ (0) − σ (∞).…”

“…According to Phillips's diffusion‐trap model, one has indeed β = D */( D * + 2) with D * = ϕD the effective dimensionality along which long‐ or short‐range active relaxation channels (with probability ϕ ) can diffuse in configurational space. The particular value for β = 0.42 found at the largest strain rate for both starting configurations (0.9 and 3%) is the one which is usually associated with only active long‐range channels ( ϕ = 1/2), driving volume relaxation …”

Mixed alkaline‐earth effects on several mechanical and thermophysical properties of aluminate glasses and melts

“…This model is supported by compelling evidence from extended X‐Ray absorption fine structure, nuclear magnetic resonance, and infrared spectroscopy, X‐ray and neutron scattering experiments in combination with reverse Monte Carlo modeling and bond‐valence sum analyses, molecular orbital calculations, molecular dynamics simulations, and theoretical works based on microscopic and semi‐microscopic approaches . Very recently, based on accelerated molecular dynamics simulations of alkali silicate glasses, Yu et al observed a bifurcation of stretched exponential decay processes for enthalpy and volume upon relaxation in the simplest mixed Na‐K silicate glasses . Combined with Phillips's topological diffusion‐trap model, they proposed a picture about the atomistic origin of mixed alkali effect, ie, the stressed local structural instabilities occur, which reach a maximum at the equal molar concentration of the two alkali atoms.…”

“…The mixed modifier effect, which manifests itself as the early known “thermometer effect” in the nineteenth century, is still attracting attention despite considerable progress in understanding this effect . For example, according to the idea of the mismatch effect from the energy landscape approach, where a site favorable for one kind of cation in the network is unfavorable for the other, the dynamic structural model has given a coherent picture about the structural origin of mixed alkali effect.…”

“…Very recently, based on accelerated molecular dynamics simulations of alkali silicate glasses, Yu et al observed a bifurcation of stretched exponential decay processes for enthalpy and volume upon relaxation in the simplest mixed Na‐K silicate glasses . Combined with Phillips's topological diffusion‐trap model, they proposed a picture about the atomistic origin of mixed alkali effect, ie, the stressed local structural instabilities occur, which reach a maximum at the equal molar concentration of the two alkali atoms.…”