Effects of fluid structure on wall pressure, interfacial tension, and surface adsorption at a spherical guest particle

Wall pressure, interfacial tension, and surface adsorption of hard and LJ fluids at the wall of a spherical guest particle were investigated in two different media (namely, a bulk fluid and one confined in a spherical pore). The MFMT theory was exploited to determine the effects of different fluid structures on the values of the above properties. Results showed that confinement mainly caused oscillations in these parameters around their corresponding bulk values such that the amplitude of the oscillations increased with increasing density but with decreasing pore size. Maximum heights of the oscillations were observed for all the three properties at each density when the pore size was around 2 times the molecular diameter. This may be due to the structure of the confined fluid that possesses a high packing factor. It was also observed that the depths and heights of the oscillations grew smaller in response to variations in the interactions of fluid molecules from a hard sphere fluid to one of LJ. Moreover, it is found that kind of interactions of the guest particle with the fluid determine the behavior of surface adsorption and interfacial tension with guest particle size. In other words, the change of guest particle-fluid interaction from a hard to an attractive one changes the signs for the slopes of surface adsorption and interfacial tension with increasing particle size.