Novikov V N, Ding Y, Sokolov A P
Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2005 Jun;71(6 Pt 1):061501. doi: 10.1103/PhysRevE.71.061501. Epub 2005 Jun 6.
We present a detailed analysis of correlations between fragility and other parameters of glass-forming systems. The analysis shows the importance of the ratio between the instantaneous bulk and shear modulus of glass-forming systems, or their Poisson ratio, for structural alpha relaxation and fast dynamics. In particular, for simple glass formers, the bulk to shear modulus ratio in the glassy state correlates with fragility in the liquid state and is inversely proportional to the intensity of the boson peak. A simple relationship between the temperature dependence of the viscosity of liquids at high temperatures and near the glass transition is used to rationalize these correlations. We argue that the ratio of the moduli controls the high-temperature activation energy of the structural relaxation and in this way affects the fragility. The ratio also defines the amplitude of the structural relaxation (i.e., the nonergodicity parameter) and the latter influences the strength of the boson peak. These observations might explain the puzzling correlation observed between the fragility and fast dynamics in glass-forming systems.
我们对玻璃形成系统的脆性与其他参数之间的相关性进行了详细分析。分析表明，玻璃形成系统的瞬时体积模量与剪切模量之比或其泊松比对于结构α弛豫和快速动力学具有重要意义。特别是对于简单的玻璃形成体，玻璃态下的体积模量与剪切模量之比与液态下的脆性相关，并且与玻色子峰的强度成反比。利用高温及接近玻璃化转变温度时液体粘度的温度依赖性之间的简单关系来解释这些相关性。我们认为，模量之比控制着结构弛豫的高温活化能，进而影响脆性。该比值还定义了结构弛豫的幅度（即非遍历性参数），而后者会影响玻色子峰的强度。这些观察结果或许可以解释在玻璃形成系统中脆性与快速动力学之间令人困惑的相关性。
