  Motivated by an experimental interest we investigate by the means of
atomistic Molecular Dynamics simulation the ability of density-independent,
empiric density-dependent, and recently proposed embedded-atom force fields for
liquid mercury to predict the surface tension of the free surface of liquid
mercury at the temperature of 293~K. The effect of the density dependence of
the studied models on the liquid-vapor coexistence and surface tension is
discussed in detail. In view of computational efficiency of the
density-independent model we optimize its functional form to obtain higher
surface tension values in order to improve agreement with experiment. The
results are also corroborated by Monte Carlo simulations and semi-analytic
estimations of the liquid-vapor coexistence density.
