Inhomogeneous pair distribution functions and wetting transitions for a model Ar-CO2interface

The modified-hypernetted-chain approximation is applied to the study of inhomogeneous transverse structure-factor and pair distribution functions for a model Ar-${\mathrm{CO}}_2$ interface. It appears that the manner in which transverse correlations decay at long range characterizes the different approach to prewetting and complete wetting. Specifically, in the approach to complete wetting, transverse correlations slowly decay with the interparticle distance in a relatively large portion of the fluid; on the other hand, when prewetting is approached, such a slow decay is found only in a confined slice. This different behavior is clearly reflected in the shape of the density profiles, which are also reported. Correlations between particles placed on a line perpendicular to the ${\mathrm{CO}}_2$ substrate are also investigated, and these show qualitative features which conform to the general picture emerging from the analysis of density profiles and transverse pair distribution functions.