Drying layer near a weakly attractive surface

Abstract

Depletion of the liquid density near a solid surface with a weak long-range fluid-surface interaction was studied by computer simulations of the liquid-vapor coexistence of a LJ fluid confined in slitlike pores. In a wide temperature range the liquid density decreases towards the surface without the formation of a {\it vapor} layer between the liquid and the solid surface. This evidences the absence of a drying transition up to the liquid-vapor critical point. Two contributions to the excess desorption {\it $\Gamma_{tot}$} were found. The first one {\it $\Gamma_{\xi}$} $\sim$ $\rho_{bulk}$ $\xi$ exists at any temperature and diverges as the bulk correlation length $\xi$ when approaching the liquid-vapor critical temperature {\it {T$_c$}}. The second contribution {\it $\Gamma_L$} $\sim$ $\rho_{bulk}$ {\it L$_0$} originates from a microscopic {\it drying layer} near the solid boundary. At high temperatures the thickness {\it L$_0$} of the drying layer increases in accordance with the power law {\it L$_0$ $\sim$ - ln (1-T/T$_c$)}, indicating a drying transition at {\it {T$_c$}}. The {\it drying layer} can be suppressed by strengthening the fluid-surface interaction, by increasing the fluid-surface interaction range or by decreasing the pore size.