长程范德华力导向作用下胶体凝聚的计算机模拟

采用计算机模拟方法研究了长程范德华力在胶体凝聚过程中的作用, 发现由于胶粒间的范德华力是长程力, 它对胶粒或团簇运动将产生导向作用. 与不考虑导向作用的扩散控制团簇凝聚(DLCA)模型比较, 这种导向作用不仅加速了胶体的凝聚过程, 而且形成了更致密、分形维数更大的结构体. 研究还发现, 长程范德华力导向作用对胶粒的初始浓度非常敏感, 不论是在凝聚物的结构还是凝聚速率方面, 只有在胶粒初始浓度较低时, 该导向作用效应才明显. 其可能的原因是,在胶粒初始浓度较高时, 由于胶粒布朗运动的平均自由程很短而且位阻效应大, 从而使导向作用效应未能反映出来.

Computer Simulation of Colloidal Aggregation Induced by Directionalism of Long Range van der Waals Forces

Colloidal aggregation within the context of long range van der Waals forces was studied by computer simulations. The motion of colloidal particles or clusters was guided by the long range van der Waals forces. Compared to the diffusion limited cluster aggregation (DLCA), which takes no account of the guiding effect, the directionalism of van der Waals forces not only accelerates the aggregation velocity but also results in morphologies of clusters with higher density and higher fractal dimensions. The directionalism arising from long range van der Waals forces was very sensitive to the initial concentration of particles. Whether on the morphology or on the aggregating velocity, the directionalism was distinct only at low initial concentration of particles. The possible reason was that, at a high particle concentration condition, both a short average random range and the steric effect of particles may screen the guiding effect.