Microphase separations of the fluids with spherically symmetric competing interactions

Abstract

A density functional perturbation theory has been developed for studying the phase behaviors of a competing system in the spherical pores. The pore size as well as the intensity of competing interactions exerts a strong influence on the vapor-liquid, vapor-cluster, and cluster-liquid transitions of a competing system. The microdomain spacing (D) of the cluster is commensurate with the periodicity of modulation in the particle density distributions of a competing system in a spherical pore with the pore radius (R). For the cluster phase, we find that the multi-vaporlike void is formed depending on the periodicity of modulation by finite-size artifacts. For R < D, the competing system only shows the vapor-liquid transition at a high amplitude. For R> D, the vapor-cluster and cluster-liquid transitions are found at a high amplitude, whereas at a low amplitude, the cluster-liquid transition only occurs. The competing system exhibits two tricritical points, which are joined to one another by the line of second-order transitions at the low and high densities. A comparison with the result of a slit pore shows that (i) the tricritical points in a spherical pore, which has the highest symmetry, occur at a low amplitude compared with that of a slit pore because of the geometrical properties of the pores, and that (ii) the slit pore relatively shows the wide vapor-cluster and cluster-liquid coexistence regions compared with that of a spherical pore: the geometrical symmetry of a pore results in a weaker tendency for phase separation.

The influence of confinement on the structure of colloidal systems with competing interactions

“…Similar studies have been performed for two dimensional system and spherical cavities. [18][19][20][21][22][23][24][25][26] The computer simulations have been performed for a lattice model 25,26 and a model with continuous potential. 18,19 Apart from simulations these systems have been studied within the density functional theory.…”

“…18,19 Apart from simulations these systems have been studied within the density functional theory. [20][21][22][23][24] The phase diagram of a three dimensional systems is richer than that of their two dimensional counterpart. Indeed some phases, such as the cylindrical hexagonal and double gyroid, do not have their analogs in 2D systems.…”