Molecular dynamics simulations of the liquid-vapor interface of a molten salt. II. Finite size effects and comparison to experiment

An examination of the finite system size effects on the calculated interfacial properties of the molten salt KI is described, as an extension of the work described in the preceding paper [J. Chem. Phys. 115, 8603 (2001)]. It is shown that, for system sizes beyond similar to 1000 ions, the finite size effects are accounted for by the predictions of capillary wave (CW) theory, as in van der Waals liquids. Hence, there do not appear to be additional long-range effects arising from the Coulombic interactions. Techniques used to avoid truncation effects in the Coulombic and dispersion interactions appear to have eliminated system size dependent artefacts from these sources. The scaling behavior predicted from CW theory is used to predict the bulk surface tension for the chosen interaction potential, which is then compared with experimental values, and very good agreement found. Examination of the interfacial layers show that the local structure remains strongly charge ordered, but the surface is highly roughened by clustering and, on longer length-scales, by the effect of capillary waves. (C) 2001 American Institute of Physics.