A study of the solidification of supercooled liquid benzophenone (BZP) is presented. As is well-known, liquid BZP can be extensively supercooled without crystallization or glass formation. In the experiments, the BZP liquid -solid phase transition is activated by either seeding or momentary freezing (using liquid nitrogen) of a portion of liquid. Measurements of the position of the liquidsolid interface as a function of time are reported. In the case of seeding, the temperature dependence of the interface propagation is examined over a range exceeding 120 K. BZP solidification is found to occur via two modes, each demonstrating its own distinct kinetics and morphology. For purposes of comparison, results of experiments with 4,4'-dimethylbenzophenone are also presented. A cellular model for BZP solidification and liquid metastability is offered.
A computation of the frequency dependent dielectric function for energetic materials AIP Conf.Temperature and frequency dependences of dielectric properties of sodium sulfate single crystal Experiment yields for many materials a dielectric loss function X"(w) having the behavior X"(w)ex:w·-I(n< I) over a substantial range of frequencies. Writing the conductivity
The two-level model of a glass of Anderson, Halperin, and Varma (AHV) is applied to calculate the dielectric relaxation loss. With the AHV model the loss function tends to a constant at low frequencies in contrast to experiment. Therefore, a modification of their probability distribution is considered, which, while retaining the essential structure, takes account of the fact that the AHV probability distribution overestimates the low frequency modes and does not therefore lead to hydrodynamic behavior. This is done by a low frequency cutoff which is shown not only to restore the correct behavior of the loss function as the frequency tends to zero but also to lead to power law behavior at intermediate frequencies as observed experimentally.
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