A density functional model for the surface properties of liquid 4He

A density functional approach is proposed to study the 4He liquid-gas interface. The free energy density, which depends on the particle density and temperature, has been adjusted to reproduce the liquid density and the vapour pressure along the liquid-gas coexistence line, as well as the zero-temperature surface tension. After achieving a fairly good description of the phase transition, the calculated surface tension agrees well with the experimental results. The calculated density profile is used to discuss a recent experimental determination of the surface thickness. (author)