An internally consistent method for the molecular dynamics simulation of the surface tension: application to some TIP4P-type models of water.

A set of molecular dynamics simulations of three members of the TIP4P model family for water (TIP4P, TIP4P/2005, TIP4P-i) are performed to illustrate the appropriate procedures to employ when simulating the planar interface between coexisting liquid and vapor phases. A method for efficiently including the long-range parts of the intermolecular dispersion interactions introduced by Janecek (J. Phys. Chem. B 2006, 110, 6264) is used. This method produces an interfacial region that is internally consistent with the dynamics of the molecules. A set of procedures are presented to verify that the surface tension estimate has converged and to obtain the underlying uncertainty of the surface tension estimate. The surface tension for the models is determined for temperatures between 300 and 550 K with an uncertainty of about 2 mN/m for this temperature range. The uncertainty is not sensitive to the temperature, but the relative uncertainty increases strongly with temperature. The surface tension is not sensitive to the system size in this temperature range provided at least 500 molecules are used, and it is shown that a thermostat does not bias the computed values.