Sarlah Andreja, Frey Erwin, Franosch Thomas
Faculty of Mathematics and Physics, Department of Physics, Univerza v Ljubljani, Jadranska 19, SI-1000 Ljubljana, Slovenia.
Phys Rev E Stat Nonlin Soft Matter Phys. 2007 Feb;75(2 Pt 1):021402. doi: 10.1103/PhysRevE.75.021402. Epub 2007 Feb 16.
Two-dimensional colloidal suspensions exposed to periodic external fields exhibit a variety of molecular crystalline phases. There two or more colloids assemble at lattice sites of potential minima to build new structural entities, referred to as molecules. Using the strength of the potential and the filling fraction as control parameters, a phase transition to unconventional orientationally ordered states can be induced. We introduce an approach that focuses at the discrete set of orientational states relevant for the phase ordering. The orientationally ordered states are mapped to classical spin systems. We construct effective Hamiltonians for dimeric and trimeric molecules on triangular lattices suitable for a statistical mechanics discussion. A mean-field analysis produces a rich phase behavior which is substantiated by Monte Carlo simulations.
暴露于周期性外场的二维胶体悬浮液会呈现出多种分子晶相。在这些晶相中，两个或更多的胶体在势能极小值的晶格位置聚集，形成新的结构实体，即所谓的分子。以势能强度和填充率作为控制参数，可以诱导出向非常规取向有序状态的相变。我们引入一种方法，该方法聚焦于与相序相关的离散取向状态集。将取向有序状态映射到经典自旋系统。我们为三角形晶格上的二聚体和三聚体分子构建了适合统计力学讨论的有效哈密顿量。平均场分析产生了丰富的相行为，蒙特卡罗模拟证实了这一点。
