The phase diagram of charge-polydisperse colloids: A Monte Carlo study

Abstract

The effect of charge polydispersity (CPD) on structural ordering of dilute charged aqueous colloidal suspensions is investigated using Monte Carlo simulations as a function of impurity-ion concentration (ni) and CPD. The behaviours of the pair correlation function, mean square displacement and total interaction energy as functions of CPD and ni are investigated to identify different phases. Crystalline order is found to transform into a glass-like order beyond a critical CPD. Both the crystalline and glassy orders are found to melt when ni is increased. The transitions between the crystalline, glassy and liquid-like phases are characterized. The phase diagram as a function of CPD and ni is reported. Colloidal crystals with finite CPD are found to melt at ni lower than that corresponding to the monodisperse (zero-CPD) suspension. The behaviour of the phase boundaries is discussed.