Kong Minghui, Partoens B, Peeters F M
Departement Natuurkunde, Universiteit Antwerpen (UIA), Universiteitsplein 1, B-2610 Antwerpen, Belgium.
Phys Rev E Stat Nonlin Soft Matter Phys. 2003 Feb;67(2 Pt 1):021608. doi: 10.1103/PhysRevE.67.021608. Epub 2003 Feb 27.
The configurational and melting properties of large two-dimensional (2D) clusters of charged classical particles interacting with each other via the Coulomb potential are investigated through the Monte Carlo simulation technique. The particles are confined by a harmonic potential. For a large number of particles in the cluster (N>150), the configuration is determined by two competing effects, namely, the fact that in the center a hexagonal lattice is formed, which is the groundstate for an infinite 2D system, and the confinement that imposes its circular symmetry on the outer edge. As a result, a hexagonal Wigner lattice is formed in the central area while at the border of the cluster the particles are arranged in rings. In the transition region defects appear as dislocations and disclinations at the six corners of the hexagonal-shaped inner domain. Many different arrangements and types of defects are possible as metastable configurations with a slightly higher energy. The particle motion is found to be strongly related to the topological structure. Our results clearly show that the melting of the clusters starts near the geometry induced defects, and that three different melting temperatures can be defined corresponding to the melting of different regions in the cluster.
通过蒙特卡罗模拟技术研究了通过库仑势相互作用的带电经典粒子的大型二维（2D）团簇的构型和熔化特性。粒子受谐振子势约束。对于团簇中大量的粒子（N>150），构型由两种相互竞争的效应决定，即中心形成六边形晶格（这是无限二维系统的基态）以及在外边缘施加其圆对称性的约束。结果，在中心区域形成了六边形维格纳晶格，而在团簇边界处粒子排列成环。在过渡区域，缺陷以六边形内域六个角处的位错和 disclinations 的形式出现。作为能量略高的亚稳构型，存在许多不同的排列和类型的缺陷。发现粒子运动与拓扑结构密切相关。我们的结果清楚地表明，团簇的熔化始于几何诱导缺陷附近，并且可以定义三个不同的熔化温度，分别对应于团簇中不同区域的熔化。
