  We investigate the liquid-vapor interface of the restricted primitive model
for an ionic fluid using a density functional approach. The applied theory
includes the electrostatic contribution to the free energy functional arising
from the bulk energy equation of state and the mean spherical approximation for
a restricted primitive model, as well as the associative contribution, due to
the formation of pairs of ions. We compare the density profiles and the values
of the surface tension with previous theoretical approaches.
