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arXiv 1606.02885cond-mat.softcond-mat.stat-mechphysics.comp-ph
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团簇晶体的形核与结构生长

Nucleation and structural growth of cluster crystals

Christian Leitold, Christoph Dellago

摘要:

本文在指数n=4的广义指数模型中研究了团簇晶相的形核过程。由于零分离的这对势的有限值,在高密度下,系统形成具有多个占据的晶格位置的簇晶体。在这里,我们调查的微观机制,导致从一个过冷液体在相图的低温区域的簇晶体的形成。使用分子动力学和伞采样,我们计算的自由能作为系统中最大的结晶核的大小的函数,并比较我们的结果与经典成核理论的预测。采用键序参量的基础上的Voronoi镶嵌来区分不同的晶体结构,我们分析了平均组成的晶核。我们发现,即使在多占据的面心立方晶体是结晶稳定相的条件下,成核成体心立方簇晶体是强烈的首选。此外,我们还研究了粒子在过冷液体和团簇晶体中的迁移率。在团簇晶体中,单个粒子的运动被一个简单的反应-扩散模型捕获,该模型先前引入来模拟氢键的动力学。

英文摘要:

We study the nucleation of crystalline cluster phases in the generalized exponential model with exponent n=4. Due to the finite value of this pair potential for zero separation, at high densities the system forms cluster crystals with multiply occupied lattice sites. Here, we investigate the microscopic mechanisms that lead to the formation of cluster crystals from a supercooled liquid in the low-temperature region of the phase diagram. Using molecular dynamics and umbrella sampling, we calculate the free energy as a function of the size of the largest crystalline nucleus in the system, and compare our results with predictions from classical nucleation theory. Employing bond-order parameters based on a Voronoi tessellation to distinguish different crystal structures, we analyze the average composition of crystalline nuclei. We find that even for conditions where a multiply-occupied fcc crystal is the thermodynamically stable phase, the nucleation into bcc cluster crystals is strongly preferred. Furthermore, we study the particle mobility in the supercooled liquid and in the cluster crystal. In the cluster crystal, the motion of individual particles is captured by a simple reaction-diffusion model introduced previously to model the kinetics of hydrogen bonds.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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