Molecular dynamics study of homogeneous and inhomogeneous phase in charged colloids: The influence of surface charge density

Compared with previous Mote Carlo (MC) simulations with 432 particles, molecular dynamics (MD) simulations with much larger number of particles have been carried out to investigate the dynamic process of the structural ordering and voids formation in charge stabilized colloidal suspensions. Sogami and Ise (SI) potential which has a long-range attraction is used to represent the interaction between colloidal particles. As increasing the surface charge density on the colloidal particles, the data obtained from the simulations, such as the crystallization, bcc–fcc phase transition, homogeneous to inhomogeneous transition and the voids formation, are in agreement with previous observations of MC simulations and experiments. The effects of particle number used in the simulations are studied in detail. MD simulations in highly charged colloidal system with small sizes show very few crystallized particles, in accord with the results of MC simulations. However, the structure in the system with larger number of particles is always the voids coexisting crystallites instead of a glasslike or disordered inhomogeneous phase, indicating that the glasslike or disordered phase region obtained at very high charge density in small system is an artifact produced by very limited number of particles used in the simulations. Therefore, SI potential is not applicable for explaining the reentrant transition of highly charged colloidal systems.