Institute of Physics, University of Silesia in Katowice, ul. 75 Pulku Piechoty 1, 41-500 Chorzow, Poland.
Silesian Center for Education and Interdisciplinary Research, ul. 75 Pulku Piechoty 1a, 41-500 Chorzow, Poland.
Int J Mol Sci. 2022 Apr 20;23(9):4546. doi: 10.3390/ijms23094546.
In this paper, we show that a simple anisotropic model of supercooled liquid properly reflects some density scaling properties observed for experimental data, contrary to many previous results obtained from isotropic models. We employ a well-known Gay-Berne model earlier parametrized to achieve a supercooling and glass transition at zero pressure to find the point of glass transition and explore volumetric and dynamic properties in the supercooled liquid state at elevated pressure. We focus on dynamic scaling properties of the anisotropic model of supercooled liquid to gain a better insight into the grounds for the density scaling idea that bears hallmarks of universality, as follows from plenty of experimental data collected near the glass transition for different dynamic quantities. As a result, the most appropriate values of the scaling exponent γ are established as invariants for a given anisotropy aspect ratio to successfully scale both the translational and rotational relaxation times considered as single variable functions of density/temperature. These scaling exponent values are determined based on the density scaling criterion and differ from those obtained in other ways, such as the virial-potential energy correlation and the equation of state derived from the effective short-range intermolecular potential, which is qualitatively in accordance with the results yielded from experimental data analyses. Our findings strongly suggest that there is a deep need to employ anisotropic models in the study of glass transition and supercooled liquids instead of the isotropic ones very commonly exploited in molecular dynamics simulations of supercooled liquids over the last decades.
在本文中，我们展示了一个简单的各向异性过冷液体模型，与许多以前从各向同性模型获得的结果相反，该模型恰当地反映了实验数据中观察到的一些密度标度性质。我们采用了一个著名的 Gay-Berne 模型，该模型之前已经被参数化，以在零压力下实现过冷和玻璃化转变，从而找到玻璃化转变点，并在高压下探索过冷液体状态的体积和动态性质。我们专注于各向异性过冷液体模型的动态标度性质，以更好地了解具有普遍性特征的密度标度思想的基础，这是从大量在玻璃化转变附近收集的不同动态量的实验数据中得出的。结果，建立了最适当的标度指数γ值作为各向异性比的不变量，成功地对作为密度/温度的单一变量函数的平移和旋转弛豫时间进行标度。这些标度指数值是基于密度标度准则确定的，与从其他方法获得的值不同，例如从有效短程分子间势能导出的 Virial 势能量相关和状态方程，这与从实验数据分析得出的结果定性一致。我们的研究结果强烈表明，在研究玻璃化转变和过冷液体时，非常有必要采用各向异性模型，而不是过去几十年来在过冷液体分子动力学模拟中非常常用的各向同性模型。
