Treatment of electrostatic interactions in simulations of the interface between transition metal surfaces and organic matter: the discrete classical model and the reaction-field dielectric method.

A more efficient molecular dynamics model is devised to study the interface between platinum(111) and liquid isopropanol. The faster reaction-field dielectric method (RFD) is investigated as the alternative to the very accurate discrete classical model (DCM) (M. W. Finnis, Surf. Sci., 1991, 241, 61) to account for the electrostatic interactions at the interface. Differences in static and dynamic properties of the interface are examined. The mass-density and number-density distributions showed only a little sensitivity towards the choice of the method. The orientational structure revealed notable but still small quantitative changes for highly-polarized parts of the isopropanol molecules if the RFD is used instead of the DCM. The general qualitative picture is still preserved. The simulations of the platinum(111)/isopropanol interface with the DCM or the Ewald summation were carried out for longer times than in our previous contribution (K. B. Tarmyshov and F. Müller-Plathe, J. Chem. Phys., 2007, 126, 74702). The analysis disclosed that the influence of chemical or electrostatic interactions at the interface on the relative orientation of the neighbouring hydroxyl groups, which are adsorbed on the surface, is notably smaller than reported before. Overall, the reaction-field dielectric method can be used to study the properties of the interface between transition metals and organic matter, if there appears a chemical bond of 10 kT or higher between the surface and adsorbate molecules or their parts.