DENSITY-FUNCTIONAL CALCULATIONS FOR HE-4 DROPLETS

A novel density functional, which accounts correctly for the equation of state, the static response function and the phonon-roton dispersion in bulk liquid helium, is used to predict static and dynamic properti es of helium droplets. The static density profile is found to exhibit significant oscillations, which are accompanied by deviations of the e vaporation energy from a liquid drop behaviour in the case of small dr oplets. The connection between such oscillations and the structure of the static response function in the liquid is explicitly discussed. Th e energy and the wave function of excited states are then calculated i n the framework of time dependent density functional theory. The new f unctional, which contains backflow-like effects, is expected to yield quantitatively correct predictions for the excitation spectrum also in the roton wave-length range.