Liquid-gas phase behavior of polydisperse dipolar hard-sphere fluid: Extended thermodynamic perturbation theory for central force associating potential

TL;DR

This paper extends thermodynamic perturbation theory to analyze the liquid-gas phase behavior of polydisperse dipolar hard-sphere fluids, revealing how polydispersity influences phase stability and coexistence.

Contribution

The study introduces an extended TPT-CF approach for polydisperse dipolar hard-sphere fluids, connecting phase behavior with particle size and dipole moment polydispersity.

Findings

Polydispersity enlarges the phase instability region.

Critical temperature and density increase with polydispersity.

Size fractionation occurs with larger particles in the liquid phase.

Abstract

The liquid-gas phase diagram for polydisperse dipolar hard-sphere fluid with polydispersity in the hard-sphere size and dipolar moment is calculated using extension of the recently proposed thermodynamic perturbation theory for central force (TPT-CF) associating potential. To establish the connection with the phase behavior of ferrocolloidal dispersions it is assumed that the dipole moment is proportional to the cube of the hard-sphere diameter. We present and discuss the full phase diagram, which includes cloud and shadow curves, binodals and distribution functions of the coexisting daughter phases at different degrees of the system polydispersity. In all cases studied polydispersity increases the region of the phase instability and shifts the critical point to the higher values of the temperature and density. The larger size particles always fractionate to the liquid phase and the smaller size particles tend to move to the gas phase. At relatively high values of the system polydispersity three-phase coexistence is observed.