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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.

We performed extensive molecular dynamics simulations to obtain pressure-density phase diagram, orientational order parameter, pair correlation functions and translational diffusion coefficients of Gay-Berne fluids. Different sets of parameters were employed for the Gay-Berne potential, in particular we studied the cases $\kappa'=5, 10, 15, 20$ and $\kappa=3$, $\mu=2$, $\nu=1$ at different conditions of density and temperature. The structure was analyzed in terms of the order parameter and the pair correlation functions. We found that for the highest value $\kappa'=20$ the region where pressure increases with density is significantly reduced at low temperatures; additionally the pressure shows several decays with density as an indicative that several structural phases can take place. These effects are discussed in terms of the pair correlation functions. For higher temperatures the pressure shows only two decays for all $\kappa'$'s studied. As this parameter increases its value those decays are shifted to lower densities., Comment: 28 pages, 9 figures