Surface tension of water and acid gases from Monte Carlo simulations

We report direct Monte Carlo ( MC ) simulations on the liquid-vapor interfaces of pure water, carbon dioxide, and hydrogen sulfide. In the case of water, the recent TIP4P/ 2005 potential model used with the MC method is shown to reproduce the experimental surface tension and to accurately describe the coexistence curves. The agreement with experiments is also excellent for CO2 and H2S with standard nonpolarizable models. The surface tensions are calculated by using the mechanical and the thermodynamic definitions via profiles along the direction normal to the surface. We also discuss the different contributions to the surface tension due to the repulsion-dispersion and electrostatic interactions. The different profiles of these contributions are proposed in the case of water. (c) 2008 American Institute of Physics.