We present a comparative study of the free surface of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ at zero temperature using phenomenological density functionals. The functional for each fluid is adjusted on experimentally known properties; the surface profile is then obtained variationally. Simple analytical formulas are derived for the relevant quantities characterizing the surface. Our results are compared with other available theoretical calculations.

• Received 14 April 1987

DOI:https://doi.org/10.1103/PhysRevB.36.8369