Relaxation in glassforming liquids and amorphous solids

Abstract

The field of viscousliquid and glassysolid dynamics is reviewed by a process of posing the key questions that need to be answered, and then providing the best answers available to the authors and their advisors at this time. The subject is divided into four parts, three of them dealing with behavior in different domains of temperature with respect to the glass transition temperature, Tg,and a fourth dealing with "short time processes. " The first part tackles the high temperature regime T>Tg, in which the system is ergodic and the evolution of the viscousliquid toward the condition at Tg is in focus. The second part deals with the regime T∼Tg, where the system is nonergodic except for very long annealing times, hence has time-dependent properties (aging and annealing). The third part discusses behavior when the system is completely frozen with respect to the primary relaxation process but in which secondary processes, particularly those responsible for "superionic" conductivity, and dopart mobility in amorphous silicon, remain active. In the fourth part we focus on the behavior of the system at the crossover between the low frequency vibrational components of the molecular motion and its high frequency relaxational components, paying particular attention to very recent developments in the short time dielectric response and the high Qmechanical response. The field of viscous liquid and glassy solid dynamics is reviewed by a process of posing the key questions that need to be answered, and then providing the best answers available to the authors and their advisors at this time. The subject is divided into four parts, three of them dealing with behavior in different domains of temperature with respect to the glass transition temperature, T g , and a fourth dealing with ''short time processes.'' The first part tackles the high temperature regime TϾT g , in which the system is ergodic and the evolution of the viscous liquid toward the condition at T g is in focus. The second part deals with the regime TϳT g , where the system is nonergodic except for very long annealing times, hence has time-dependent properties ͑aging and annealing͒. The third part discusses behavior when the system is completely frozen with respect to the primary relaxation process but in which secondary processes, particularly those responsible for ''superionic'' conductivity, and dopart mobility in amorphous silicon, remain active. In the fourth part we focus on the behavior of the system at the crossover between the low frequency vibrational components of the molecular motion and its high frequency relaxational components, paying particular attention to very recent developments in the short time dielectric response and the high Q mechanical response.

Pressure-energy correlations in liquids. V. Isomorphs in generalized Lennard-Jones systems

“…[8][9][10][11][12][13][14][15][16][17][18] Thus it has been shown that strongly correlating viscous liquids to a good approximation have all eight frequency-dependent thermoviscoelastic response functions [19][20][21] given in terms of just one 22 (i.e., are single-parameter liquids in the sense of having dynamic Prigogine-Defay ratio 19 close to unity 2,20,22 ). Strongly correlating viscous liquids moreover obey density scaling [23][24][25][26][27] to a good approximation, i.e., their dimensionless relaxation timeτ ≡ τρ 1/3 √ k B T /m (where m is the average particle mass) depends on density ρ = N /V and temperature as τ = F(ρ γ /T ).…”

Ion migration in crystalline and amorphous HfOX

“…In order to examine the stability of the amorphous phases and to ensure that no structural relaxations are present, as mentioned by Angell et al, 44 we subjected the simulation cells to a quasi-static thermal cycle, in which the system was equilibrated at a range of (first increasing, then decreasing) temperatures. In Fig.…”

The Microscopic Quantum Theory of Low Temperature Amorphous Solids

“…For a review, see (Angell et al, 2000;Böhmer et al, 1993). A specific example of a τ (T ) dependence is shown in the l.h.s.…”