Attractive hard-core Yukawa fluids in the nanosized pores: Structure and phase behaviors

Abstract

A density functional perturbation theory has been developed for studying the structure and phase behaviors of an attractive hard-core Yukawa fluid in the nanosized slit and spherical pores at the subcritical temperature. The calculated results show that the pore geometry and size strongly affect on the liquid–vapor coexistence curve and critical point of a confined attractive hard-sphere Yukawa fluid. For the value of the chemical potential corresponding to a stable liquid phase in the bulk system and a metastable vapor phase, an attractive hard-core Yukawa fluid undergoes a phase transition as the slit width (or the pore radius) is reduced whereby the vapor phase becomes the preferred state at the narrow slit pores (or the small volumes), whereas the liquid is the stable phase at the wide slit pores (or the large volumes). The wide adsorption/desorption curve, which implies the wide range of metastable liquid–vapor states, is observed at a low temperature. The increase of the slit width (or the pore radius) leads to a wider adsorption/desorption curve, whereas the increase of the temperature leads to a narrower liquid–vapor coexistence curve. The critical point in a slit pore is shifted towards a lower temperature compared with that of the bulk phase, i.e., the confinement moves the transition towards a higher chemical potential. The critical point in a spherical pore occurs at a lower temperature compared with that of a slit pore.