Development of nano-structured material based on computer simulation of rod-like particles

近年来纳米技术的发展认识到纳米尺度结构控制的重要性。棒状和盘状硬颗粒呈现出不同的液晶结构，表明利用纳米级硬颗粒分散体控制纳米结构的可能性。在这个项目中，我们计划用计算机模拟研究棒状粒子和圆盘状粒子构成的结构。我们还计划了一些实验，通过添加棒状颗粒或棒状分子来检验材料性能的控制。球形柱体是一种表示棒状粒子的模型。它是一个圆柱体，每个圆柱体的两端都有一个半球。它的形状是通过在线段上扫过球体的中心来确定的。在本课题中，我们提出了一种新型的模型粒子——球形圆盘。它是将球圆柱体延伸成圆盘状。它的形状是通过扫过圆盘上的球体中心来确定的。研究了平行硬球柱和硬球二元混合物的蒙特卡罗模拟结果，提出了混合物状态方程的近似形式。分子动力学模拟表明，近晶层结构的形成干扰了分子在层间的扩散。单分散硬球盘的模拟结果表明，盘状颗粒具有很强的成柱亲和性。仿真快照显示了全局各向同性结构中的局部柱结构。在蒙特卡罗模拟中，观察到不同直径的硬球盘二元混合物中存在分散的柱状团簇。

Recent development of nanotechnology recognizes importance of control of nano-scale structure. The fact that rod-like and disc-like hard particles show various liquid crystal structures indicates possibility of control of nano-structure by using dispersions of nano-scale hard particles. In this project we planned computer simulations that studied structures made by rod-like particles and disc-like particles. We also planned experiments with which we examined control of material property by adding rod-like particles or rod-like molecules.Spherocylinder is a model representing a rod-like particle. It is a cylinder each end of which is capped with a hemisphere. Its shape is determined by a sweep of the center of a sphere on a line segment. In this research project, we proposed novel type of model particle named spherical disc. It is an extension of the spherocylinder to a disc-like shape. Its shape is determined by a sweep of the center of a sphere on a disc.We examined results of Monte Carlo simulation of binary mixtures of parallel hard spherocylinders and hard spheres to propose an approximation form of equation-of-state of the mixtures. Molecular dynamics simulation of the mixtures shows that formation of smectic layer structure disturbs interlayer diffusion of molecules.Simulation results of monodisperse hard spherical discs indicates that disc-like particles show strong affinity to form columns. Simulation snapshots show local column structures in global isotropic structures. Dispersed column clusters of discs is observed in Monte Carlo simulation of binary mixtures of hard spherical discs of different diameters.