带电粒子形成胶体晶体的有效硬球模型判据的计算机模拟验证

在对胶体晶体的研究中,带电粒子胶体晶体的形成机理比硬球胶体晶体更加复杂,对其形成条件目前还缺少有效的判断依据. 有效硬球模型判据提出以有效直径作为判断参数. 为了验证该判据的有效性,利用布朗动力学模拟研究了不同有效直径下带电粒子胶体晶体的特性. 为了更加定量地研究单因素对带电胶体晶体形成的影响,取有效直径为2.8至0.8,并对一定的有效直径,研究了粒子几何直径和排斥力不同情况下的结晶行为. 在布朗动力学模拟过程中,采用径向分布函数和键序参数方法检测体系的结构变化,并分析所形成的晶体结构. 结果表明,在判断带电粒子胶体体系能否形成有序结构方面,有效硬球模型判据有一定的合理性. 但是,并不能将有效直径作为唯一的判别参数,而是需要综合其他参数的影响,这显示出该判据的片面性. 关键词： 布朗动力学模拟 带电胶体晶体 有效硬球模型

A Brownian dynamic simulation to verify the effective hard-sphere model criterion for the formation of charged colloidal crystals

The mechanism for the formation of colloidal crystals in charge-stabilized colloids is more complicated than that of hard-sphere colloidal crystals. And there is still lack of available criterion for the formation of charged colloidal crystals. The effective hard-sphere model suggests a criterion in which the effective diameter is used as a crucial parameter. In order to test the validity of this criterion, the characteristics of charged colloidal crystals with different effective diameters are investigated using Brownian dynamics simulations in this study. The crystallization behaviors with different geometric particle diameters and repulsive forces are also studied with some fixed effective diameters. In the simulation, the time evolution of crystallization process and the crystal structure during the simulation are characterized by means of the radial distribution functions and bond-order parameters. The results show that the effective hard-sphere model criterion has its reasonableness to some extent. However, the effective diameter cannot be used as the only parameter that influences the formation of charged colloidal crystals. The influence of other parameters should also be taken into account, which indicates that the criterion is one-sided.