Narrow Results

Adsorbed films of liquid ⁴He are analized, in the framework of Density Functional Theories (DF). In these systems, when the substrate becomes increasingly attractive, the thin films of ⁴He approaches the quasi-bidimensional limit. We study this strongly attractive substrate regime with two DF, the Orsay-Trento (OT) and a recent Hybrid proposal (Hyb), focusing in the energy behavior. It is showed that OT does not reproduce the correct limiting energy curve, and it implies that this functional could not provide reliable results for very strongly attractive substrates like Graphite (Gr). In other hand, with the Hyb DF, the correct energy behavior is found for the adsorption energy of ⁴He on Gr. These results show that OT should not be applied to quasi 2D (confinement) situations, and that Hyb DF provides a much more realistic description.

Diffusion Monte Carlo calculations on the adsorption of ⁴He inside carbon nanotubes are presented. We focused on the (10,10) ones, in which a ground state liquid phase at low densities and pressures around zero. In those calculations, all the carbon atoms where considered individually, both in the trial function and in their contribution to the total potential. Comparisons are made with the liquid state of helium inside a (5,5) carbon nanotube.