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arXiv 0811.1117cond-mat.soft
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过冷二元液体混合物的稳定性

Stability of supercooled binary liquid mixtures

Søren Toxvaerd, Ulf R. Pedersen, Thomas B. Schrøder, Jeppe C. Dyre

摘要:

最近,在冗长的分子动力学模拟中,过冷的Wahnstrom二元Lennard-Jones混合物部分结晶为${\rm MgZn_2}$相晶体。我们提出了分子动力学模拟的修改后的Kob-Andersen二元Lennard-Jones混合物,也结晶在冗长的模拟,但在这里形成纯fcc晶体的主要组成部分。这两个发现激发本文给出了一个一般的热力学和动力学处理的过冷二元混合物的稳定性,强调负混合焓的重要性,无论何时存在。该理论被用于从一系列相关体系的结晶时间估计Kob-Andersen混合物的结晶时间。在T=0.40时,我们估计该时间为5个$\times 10^{7}$时间单位($\approx 1. ms$)。提出了一种新的二元Lennard-Jones混合物,它不容易结晶,并且比两种标准的二元Lennard-Jones混合物更快地模拟;这是通过切换到Weeks-Chandler-Andersen型势来去除相似粒子吸引力,同时保持不相似粒子吸引力来获得的。

英文摘要:

Recently the supercooled Wahnstrom binary Lennard-Jones mixture was partially crystallized into ${\rm MgZn_2}$ phase crystals in lengthy Molecular Dynamics simulations. We present Molecular Dynamics simulations of a modified Kob-Andersen binary Lennard-Jones mixture that also crystallizes in lengthy simulations, here however by forming pure fcc crystals of the majority component. The two findings motivate this paper that gives a general thermodynamic and kinetic treatment of the stability of supercooled binary mixtures, emphasizing the importance of negative mixing enthalpy whenever present. The theory is used to estimate the crystallization time in a Kob-Andersen mixture from the crystallization time in a series of relared systems. At T=0.40 we estimate this time to be 5$\times 10^{7}$ time units ($\approx 1. ms$). A new binary Lennard-Jones mixture is proposed that is not prone to crystallization and faster to simulate than the two standard binary Lennard-Jones mixtures; this is obtained by removing the like-particle attractions by switching to Weeks-Chandler-Andersen type potentials, while maintaining the unlike-particle attraction.

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