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arXiv 1407.3989cond-mat.soft
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势软度对二维核软化势系统固液相变的影响

Effect of a potential softness on the solid-liquid transition in a two-dimensional core-softened potential system

D. E. Dudalov, Yu. D. Fomin, E. N. Tsiok, V. N. Ryzhov

摘要:

本文利用分子动力学模拟方法研究了经典粒子通过纯排斥各向同性核软化势相互作用的二维($2D$)系统的熔化性质。我们发现,融化的情况下,极大地依赖于潜在的柔软性和变化的光滑排斥肩的宽度增加。当排斥肩宽度较小时,熔融转变表现出弱的一级行为,当排斥肩宽度较大时,在不太高的压力下压缩时发生折返熔融转变,在$2D$相图的低密度部分,熔融是一个连续的两阶段转变,根据Kosterlitz-Escherless-Halperin-Nelson-Young(KTHNY)方案,具有中间六方相。另一方面,在相图的高密度部分,发生一级转变。这些结果有助于定性地了解水在两个疏水板之间的行为。

英文摘要:

In the present paper, using a molecular dynamics simulation, we study a nature of melting of a two-dimensional ($2D$) system of classical particles interacting through a purely repulsive isotropic core-softened potential which is used for the qualitative description of the anomalous behavior of water and some other liquids. We show that the melting scenario drastically depends on the potential softness and changes with increasing the width of the smooth repulsive shoulder. While at small width of the repulsive shoulder the melting transition exhibits what appears to be weakly first-order behavior, at larger values of the width a reentrant-melting transition occurs upon compression for not too high pressures, and in the low density part of the $2D$ phase diagram melting is a continuous two-stage transition, with an intermediate hexatic phase in accordance with the Kosterlitz-Thouless-Halperin-Nelson-Young (KTHNY) scenario. On the other hand, at high density part of the phase diagram one first-order transition takes place. These results may be useful for the qualitative understanding the behavior of water confined between two hydrophobic plates.

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