Perturbation density functional theory and Monte Carlo simulations for the structure of hard triatomic fluids in slitlike pores

A model fluid composed of semiflexible tangent hard sphere trimers is investigated using Monte Carlo simulations and perturbation density functional theory (PDFT), focusing on the density profile and conformational properties in the vicinity of a hard wall. The surface density is reduced (enhanced) at low (high) densities. We also observe preferential end absorption. Both features arise from competition between chain conformational entropy and packing constraints. Molecules adjacent to the wall tend to lie flat against it, particularly at high density and/or stiffness. But the bond angle distribution is only weakly affected by the presence of the wall. For rigid molecules, the density profiles depend strongly on the value of the bond angle. PDFT is in excellent agreement with simulation, and promises to be a successful means of elucidating the interfacial structure of complex fluids.