Hard-sphere fluids in very narrow cylindrical pores

Properties of fluids in narrow pores have been studied extensively in recent years. In this paper, we study the pore radius dependence of hard-sphere fluids in very narrow cylindrical pores via Monte Carlo simulations to explore the crossover from strictly one-dimensional to quasi-one-dimensional fluids. Our study shows that this crossover is not simple. We observe, for constant pressure, an unexpected but interesting nonmonotonic variation of density and compressibility as the pore radius is varied near the value of one hard-sphere diameter ${\mathrm{(\sigma }}_{\mathrm{hs}}\mathrm{).}$ These results are related to the onset of configurations with two or more nearest-neighbor hard spheres across the diameter of the cylindrical pore.