Institute of Physics, University of Rostock, Wismarsche Str. 43-45, 18057 Rostock, Germany.
J Chem Phys. 2012 Feb 21;136(7):074512. doi: 10.1063/1.3685510.
An overview on different attempts of formulation of kinetic criteria of glass formation is given. It is analyzed which of the characteristic time scales-time of observation, time of relaxation, and time of change of external parameters-have to be employed to appropriately develop such criteria. Based on this analysis, a general model-independent kinetic criterion for glass formation is formulated. As a first consequence, it is shown that it is not-as often claimed-the Deborah number which governs glass formation. Based on this general kinetic criterion for glass formation, general expressions for the dependence of the glass transition temperature on pressure (and vice versa) are obtained being essentially ratios of the partial derivatives of the appropriate relaxation times with respect to pressure and temperature, respectively. Employing, as examples, further two different (free volume and entropy based) models for the description of viscous flow and relaxation, respectively, relations similar but, in general, not identical to the classical Ehrenfest relations describing second-order equilibrium phase transitions are obtained. In this way, it can be explained why one of the Ehrenfest's relations is usually fulfilled in glass transition and the other not and why the Prigogine-Defay ratio in glass transition is not equal to one as this is the case with Ehrenfest's ratio in second-order equilibrium phase transitions.
给出了对玻璃形成动力学判据的不同尝试的概述。分析了哪些特征时间尺度——观察时间、弛豫时间和外部参数变化时间——必须用于适当发展此类判据。基于此分析，提出了一种通用的无模型动力学玻璃形成判据。作为第一个结果，证明了控制玻璃形成的不是通常所声称的 Deborah 数。基于这种通用的玻璃形成动力学判据，得到了玻璃化转变温度对压力（反之亦然）的依赖关系的一般表达式，它们本质上是相应弛豫时间相对于压力和温度的偏导数的比值。以进一步的两个不同的（自由体积和熵）模型为例，分别用于描述粘性流动和弛豫，得到了类似于描述二阶平衡相变的 Ehrenfest 关系的关系，但通常并不相同。通过这种方式，可以解释为什么 Ehrenfest 关系中的一个通常在玻璃化转变中得到满足，而另一个则没有，以及为什么在玻璃化转变中 Prigogine-Defay 比不等于 Ehrenfest 比在二阶平衡相变中。
