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arXiv 1903.06313cond-mat.softcond-mat.stat-mech
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偶极硬球模型的滞止动力学

Arrested dynamics of the dipolar hard-sphere model

Luis Fernando Elizondo-Aguilera, Ernesto Carlos Cortés-Morales, Pablo F. Zubieta Rico, Magdaleno Medina-Noyola, Ramón Castañeda-Priego, Thomas Voigtmann, Gabriel Pérez-Ángel

摘要:

我们报告的综合结果的分子动力学模拟和理论计算的各种动力学逮捕过渡的模型系统中的偶极流体,即N(软核)刚性球通过截断偶极-偶极势相互作用。通过探索不同的制度的浓度和温度,我们发现三个不同的情况下的平移和取向的自由度的动力学减慢:在低({ $η$ } = 0.2)和中间($η$ = 0.4)的体积分数,这两个动力学强烈耦合,并成为同时逮捕冷却后。在高浓度({ $η$ } $\lt$ 0.6),平移动力学显示的功能,一个普通的玻璃化转变,无论是通过压缩或冷却系统,但与取向保持遍历,从而表明存在的部分逮捕状态。在此密度范围内,但在较低的温度下,取向动力学的弛豫也冻结。由模拟提供的物理场景进行了讨论和比较与自洽广义朗之万方程理论得到的结果,都提供了一个一致的描述系统中的动态逮捕过渡。我们的研究结果总结在逮捕状态图定性组织的模拟数据,并提供了一个通用的图片的偶极流体的玻璃化转变。

英文摘要:

We report the combined results of molecular dynamics simulations and theoretical calculations concerning various dynamical arrest transitions in a model system representing a dipolar fluid, namely, N (softcore) rigid spheres interacting through a truncated dipole-dipole potential. By exploring different regimes of concentration and temperature, we find three distinct scenarios for the slowing down of the dynamics of the translational and orientational degrees of freedom: At low ({$η$} = 0.2) and intermediate ($η$ = 0.4) volume fractions, both dynamics are strongly coupled and become simultaneously arrested upon cooling. At high concentrations ({$η$} $\lt$ 0.6), the translational dynamics shows the features of an ordinary glass transition, either by compressing or cooling down the system, but with the orientations remaining ergodic, thus indicating the existence of partially arrested states. In this density regime, but at lower temperatures, the relaxation of the orientational dynamics also freezes. The physical scenario provided by the simulations is discussed and compared against results obtained with the self-consistent generalized Langevin equation theory, and both provide a consistent description of the dynamical arrest transitions in the system. Our results are summarized in an arrested states diagram which qualitatively organizes the simulation data and provides a generic picture of the glass transitions of a dipolar fluid.

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