期刊
PHYSICAL REVIEW E
卷 61, 期 2, 页码 1783-1792出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevE.61.1783
关键词
-
Experimental data for the temperature dependence of relaxation times are used to argue that the dynamic scaling form, with relaxation time diverging at the critical temperature T-c as (T- T-c)(-vz), is superior to the classical Vogel form. This observation leads us to propose that glass formation can be described by a simple mean-field limit of a phase transition. The order parameter is the fraction of all space that has sufficient free volume to allow substantial motion, and grows logarithmically above T-c. Diffusion of this free volume creates random walk clusters that have cooperatively rearranged. We show that the distribution of cooperatively moving clusters must have a Fisher exponent r=2. Dynamic scaling predicts a power law for the relaxation modulus G(t)similar to t(-2/z), where z is the dynamic critical exponent relating the relaxation time of a cluster to its size. Andrade creep, universally observed for all glass-forming materials, suggests z=6. Experimental data on the temperature dependence of viscosity and relaxation time of glass-forming liquids suggest that the exponent v describing the correlation length divergence in this simple scaling picture is not always universal. Polymers appear to universal have vz=9 (making v=3/2,). However, other glass-formers have unphysically large values of vz, suggesting that the availability of free volume is a necessary, but not sufficient, condition for motion in these liquids. Such considerations lead us to assert that vz=9 is in fact universal for all glass-forming liquids, but an energetic barrier to motion must also be overcome for strong glasses.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据