Symmetry Breaking of the Fluid Density Profiles in Closed Nanoslits *

The density profiles in a fluid interacting with the two identical solid walls of a closed long slit were calculated for wide ranges of the number of fluid molecules in the slit and temperature by employing a nonlocal density functional theory. Using argon as the sample fluid and considering the walls composed of solid carbon dioxide, it is shown that the density profile corresponding to the stable state of the fluid considerably changes its shape with increasing average density ρ _av of the fluid inside the slit. Temperature dependent critical values ρ_{sb 1}and ρ_{sb 2}of ρ _av were identified, such that for ρ_{sb 1} ⩽ ρ _av ⩽ ρ_{sb 2}the stable state of the system is described by an asymmetric density profile whereas outside this range it is described by a symmetric one. Hence a spontaneous symmetry breaking of the fluid density distribution in a closed slit with identical walls can take place. On the basis of the results obtained for closed slits, the symmetry breaking in open slits was also examined. © 2007 American Institute of Physics. [DOI: 10.1063/1.2715934]