MD Simulations of Charged Binary Mixtures Reveal a Generic Relation Between High- and Low-Temperature Behavior
L. Hecht, R. Horstmann, B. Liebchen, M. Vogel
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This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in J. Chem. Phys. 154, 024501 (2021) and may be found at https://doi.org/10.1063/5.0031417
Experimental studies of the glassy slowdown in molecular liquids indicate that the high-temperature activation energy $E_{\infty}$ of glass-forming liquids is directly related to their glass transition temperature $T_{\text{g}}$. 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 (MD) 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 $E_{\infty}$ and $T_{\text{g}}$, 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 $T_{\text{g}}$. 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 $E_{\infty}$ may allow to approximately predict $T_{\text{g}}$.
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Chemical potentials from structure factors: II. Charged multi-component mixtures
Department of Chemistry, UC Berkeley（加州大学伯克利分校化学系）；Chemical Sciences Division, Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室化学科学部）；Bakar Institute of Digital Materials for the Planet, UC Berkeley（加州大学伯克利分校巴克拉行星数字材料研究所）
When simulating multicomponent mixtures via the Lattice Boltzmann Method, it is desirable to control the mutual diffusivity between species while maintaining the viscosity of the solution fixed. This goal is herein achieved by a modification of the multicomponent Bhatnagar-Gross-Krook (BGK) evolution equations by introducing two different timescales for mass and momentum diffusion. Diffusivity is thus controlled by an effective drag force acting between species. Numerical simulations confirm the accuracy of the method for neutral binary and charged ternary mixtures in bulk conditions. The simu…
