On the Hysteresis Loop of Argon Adsorption in Cylindrical Pores

We study the evolution of the hysteresis loop, its size and shape with the pore size, pore length, and closed end by GCMC simulation. It is shown that the mechanism of condensation and evaporation is essentially related to the fluid properties in the case of infinite cylindrical pores. In cylindrical pores of finite length, the hysteresis loop becomes smaller and then disappears when either the pore size or the pore length decreases according to the presence and movement of the fluid vapor interface. A major deduction from this work is that by combining isotherms of pores of different sizes, lengths, and closed ends we can simulate adsorption of isotherms similar to those of solids with complex configurations, such as inkbottle pores. We conclude that not only the pore size but also the pore length and the affinity of the closed end play important roles in determining the shape of the adsorption isotherm and should be taken into account in the characterization of pore structure from gas adsorption.