Hecht L, Horstmann R, Liebchen B, Vogel M
Institut für Physik Kondensierter Materie, Technische Universität Darmstadt, Hochschulstr. 8, 64289 Darmstadt, Germany.
Institut für Physik Kondensierter Materie, Technische Universität Darmstadt, Hochschulstr. 6, 64289 Darmstadt, Germany.
J Chem Phys. 2021 Jan 14;154(2):024501. doi: 10.1063/5.0031417.
Experimental studies of the glassy slowdown in molecular liquids indicate that the high-temperature activation energy E of glass-forming liquids is directly related to their glass transition temperature T. To further investigate such a possible relation between high- and low-temperature dynamics in glass-forming liquids, we analyze the glassy dynamics of binary mixtures using molecular dynamics simulations. We consider a binary mixture of charged Lennard-Jones particles and vary the partial charges of the particles and, thus, the high-temperature activation energy and the glass transition temperature of the system. Based on previous results, we introduce a phenomenological model describing relaxation times over the whole temperature regime from high temperatures to temperatures well inside the supercooled regime. By investigating the dynamics of both particle species on molecular and diffusive length scales along isochoric and isobaric pathways, we find a quadratic charge dependence of both E and T, resulting in an approximately constant ratio of both quantities independent of the underlying observable, the thermodynamic ensemble, and the particle species, and this result is robust against the actual definition of T. This generic relation between the activation energy and the glass transition temperature indicates that high-temperature dynamics and the glassy slowdown are related phenomena, and the knowledge of E may allow us to approximately predict T.
分子液体中玻璃态减速的实验研究表明，玻璃形成液体的高温活化能E与其玻璃化转变温度T直接相关。为了进一步研究玻璃形成液体中高温和低温动力学之间这种可能的关系，我们使用分子动力学模拟分析二元混合物的玻璃态动力学。我们考虑带电的 Lennard-Jones 粒子的二元混合物，并改变粒子的部分电荷，从而改变系统的高温活化能和玻璃化转变温度。基于先前的结果，我们引入了一个唯象模型，该模型描述了从高温到过冷区域内温度的整个温度范围内的弛豫时间。通过沿着等容和等压路径在分子和扩散长度尺度上研究两种粒子的动力学，我们发现E和T都与电荷呈二次方依赖关系，从而导致这两个量的比值近似恒定，与潜在的可观测量、热力学系综和粒子种类无关，并且这个结果对于T的实际定义是稳健的。活化能和玻璃化转变温度之间的这种普遍关系表明，高温动力学和玻璃态减速是相关现象，并且对E的了解可能使我们能够近似预测T。
