  We report the improvement of five argon force fields by scaling Lennard-Jones
energy ($\epsilon$) and distance ($\sigma$) parameters to reproduce
liquid-vapor phase diagram and surface tension simultaneously, with molecular
dynamics. Original force fields reproduce only liquid-vapor phase diagram among
other properties except surface tension. Results showed that all force fields
converge in a nearby region in the $\epsilon$-$\sigma$ phase space, which is
different from the original values. This study gives the intervals where the
numerical values of $\epsilon$ and $\sigma$ reproduce both properties mentioned
above.
