Asymmetric semi-infinite nuclear matter: surface and curvature properties in relativistic and non-relativistic models

Surface and curvature properties of asymmetric semi-infinite nuclear matter are studied to beyond the proton drip. Using the semiclassical extended Thomas–Fermi method, the calculations are performed in the non-relativistic and relativistic mean field theories (Skyrme forces and non-linear σ−ω parametrizations). First we discuss the bulk equilibrium between the nuclear and drip phases. Next we analyze the asymmetric surface as a function of the bulk neutron excess. We examine local quantities related to the density profiles and, for two definitions of the bulk reference energy, the surface and curvature energy coefficients. The calculation of the curvature energy is carefully treated. The sensitivity of the nuclear surface to the relativistic effects is investigated. Mass formulae useful for arbitrary neutron excess are discussed, and their limit at small asymmetries is compared with the liquid droplet model mass formula. PACS: 21.60.-n, 21.10.Dr, 21.65.+f