Saija Franz, Prestipino Santi, Malescio Gianpietro
CNR-Istituto per i Processi Chimico-Fisici, Contrada Papardo, 98158 Messina, Italy.
Phys Rev E Stat Nonlin Soft Matter Phys. 2009 Sep;80(3 Pt 1):031502. doi: 10.1103/PhysRevE.80.031502. Epub 2009 Sep 10.
We study the phase behavior of a classical system of particles interacting through a strictly convex soft-repulsive potential which, at variance with the pairwise softened repulsions considered so far in the literature, lacks a region of downward or zero curvature. Nonetheless, such interaction is characterized by two length scales, owing to the presence of a range of interparticle distances where the repulsive force increases, for decreasing distance, much more slowly than in the adjacent regions. We investigate, using extensive Monte Carlo simulations combined with accurate free-energy calculations, the phase diagram of the system under consideration. We find that the model exhibits a fluid-solid coexistence line with multiple re-entrant regions, an extremely rich solid polymorphism with solid-solid transitions, and waterlike anomalies. In spite of the isotropic nature of the interparticle potential, we find that among the crystal structures in which the system can exist, there are also a number of non-Bravais lattices, such as cI16 and diamond.
我们研究了一个经典粒子系统的相行为，该系统通过严格凸的软排斥势相互作用。与文献中迄今为止考虑的成对软化排斥不同，这种势缺乏向下或零曲率的区域。尽管如此，由于存在一系列粒子间距离范围，在此范围内排斥力随距离减小的增加速度比相邻区域慢得多，这种相互作用具有两个长度尺度。我们使用广泛的蒙特卡罗模拟结合精确的自由能计算，研究了所考虑系统的相图。我们发现该模型呈现出具有多个再入区域的流体 - 固体共存线、具有固 - 固转变的极其丰富的固体多晶型以及类似水的异常现象。尽管粒子间势具有各向同性，但我们发现在系统能够存在的晶体结构中，也有许多非布拉菲晶格，如体心立方I16和金刚石结构。
