胶体排空相互作用理论与计算  

Theory and calculations of colloidal depletion interaction

作　　者：马红孺[1,2] 

机构地区：[1]上海交通大学机械与动力工程学院,上海200240 [2]上海交通大学,人工结构及量子调控教育部重点实验室,上海200240

出　　处：《物理学报》2016年第18期14-27,共14页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11304169)资助的课题~~

摘　　要：胶体悬浮液由1 nm到1μm大小的颗粒悬浮在液体中构成.胶体颗粒之间具有体积排斥相互作用和其他相互作用,体积排斥导致排空效应.当大硬球处于小球构成的胶体中时,大球周围有小球中心不能进入的排空层.在大的硬球相互接近时,其排空层重合,使小球的自由体积增加,从而熵增加,导致大球之间的等效相互作用,这个相互作用称为排空相互作用.本文介绍了胶体排空相互作用的概念和图像,简要介绍了计算硬球排空相互作用的接受比率方法、Wang-Landau方法、密度泛函理论方法等数值方法;以Asakura-Oosawa模型为例,介绍了Derjaguin近似方法.利用这个近似方法,推导了小硬球胶体中一对硬球、硬球和硬墙之间的排空相互作用,以及一对硬球在细棒胶体和薄盘胶体中的排空相互作用的近似公式.Colloidal suspension is composed of particles with sizes between 1 nm and 1 μm,suspended in liquid phase.The interaction between the particles consists of a hard core repulsive interaction and other kinds of repulsive and attractive interacions.Hard interaction forbids the particles from occupying the same places,resulting in a depletion effect.When big colloid particles are immersed in a colloid of small particles,each big particle has a depletion layer where the small particles cannot enter due to the hard interaction.The depletion layers of two big particles overlap when they are close enough so that extra free volume of the small particles increases and therefore the entropy of the small particles increase,thus an effective interaction between big particles is induced.This effective interaction is the so-called depletion interaction.In this review the concepts and an intuitive explanation of depletion interaction of colloidal suspensions are presented.The numerical calculation methods,including the acceptance ratio method,Wang-Landau-type method,and density functional theory method,are briefly reviewed.Several useful analytic approximations are presented.Stating from the depletion interaction between two flat plates,the Derjaguin approximation is introduced through the AsakuraOosawa model.With this approximation,the approximate formulas of depletion interaction between two hard spheres,between a hard sphere and a hard wall,and between a hard sphere and curved hard walls in a small hard sphere colloid are derived.The depletion interaction between two hard spheres in a thin rod colloid and a thin disk colloid are also derived in the Derjaguin approximation.

关 键 词：胶体 排空相互作用 

分 类 号：O648.1[理学—物理化学]