Zangi R, Rice SA
Department of Chemistry and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics. 2000 Jan;61(1):671-81. doi: 10.1103/physreve.61.671.
We report the results of extensive molecular dynamics simulations of the reconstructive hexagonal to square lattice conversion in bilayer colloid systems. Two types of interparticle potential were used to represent the colloid-colloid interactions in the suspension. One potential, due to Marcus and Rice, is designed to describe the interaction of sterically stabilized colloid particles. This potential has a term that represents the attraction between colloid particles when there is incipient overlap between the stabilizing brushes on their surfaces, a (soft repulsion) term that represents the entropy cost associated with interpenetration of the stabilizing brushes, and a term that represents core-core repulsion. The other potential we used is an almost hard core repulsion with continuous derivatives. Our results clearly show that the character of the reconstructive hexagonal to square lattice conversion in bilayer colloid systems is potential dependent. For a system with colloid-colloid interactions of the Marcus-Rice type, the packing of particles in the square array exhibits a large interlayer lattice spacing, with the particles located at the minima of the attractive well. In this case the hexagonal to square lattice transition is first order. For a system with hard core colloid-colloid interactions there are two degenerate stable intermediate phases, linear and zigzag rhombic, that are separated from the square lattice by strong first order transitions, and from the hexagonal lattice by either weak first or second order transitions.
我们报告了双层胶体系统中从六角晶格到方形晶格重构转变的广泛分子动力学模拟结果。使用了两种类型的粒子间势来表示悬浮液中胶体 - 胶体的相互作用。一种由马库斯和赖斯提出的势，旨在描述空间稳定胶体颗粒之间的相互作用。该势有一项表示当胶体颗粒表面的稳定刷开始重叠时颗粒间的吸引力，一项（软排斥）表示与稳定刷相互渗透相关的熵成本，还有一项表示核 - 核排斥。我们使用的另一种势是具有连续导数的几乎硬核排斥势。我们的结果清楚地表明，双层胶体系统中从六角晶格到方形晶格重构转变的性质取决于势。对于具有马库斯 - 赖斯型胶体 - 胶体相互作用的系统，方形阵列中颗粒的堆积表现出较大的层间晶格间距，颗粒位于吸引阱的最小值处。在这种情况下，从六角晶格到方形晶格的转变是一级的。对于具有硬核胶体 - 胶体相互作用的系统，有两个简并的稳定中间相，线性和之字形菱形，它们通过强一级转变与方形晶格分开，通过弱一级或二级转变与六角晶格分开。
