Phase behavior of Lennard-Jones fluids in pores formed between two cylindrical walls

We study structure and phase behavior of a Lennard-Jones (12, 6) fluid adsorbed in pores with curved walls that are made of two uniaxial cylinders by using a density functional approach. The attractive wall-particle potential is an analogue of the Lennard-Jones (9, 3) potential that has been developed to model interaction of a particle with a flat wall. We also compare the results obtained for attractive pore walls with those evaluated for hard cylindrical walls. We have found that in both cases, i.e. in the case of the attractive, as well as, hard walls, the increase of the radius of curvature of the walls while keeping the distance between them constant, decreases the critical temperature of the liquid–vapor transition in the confined fluid. However, the shift of the chemical potential at the transition point is different for the pores with attractive walls and for the pores with hard walls. In the case of the walls exerting an attractive adsorbing potential, the increase of the radius of the curvature causes decrease of the chemical potential at the capillary condensation point. In the case of hard walls the increase of the radius of the curvature leads to an increase of the chemical potential at the capillary evaporation point.