Surface energy and surface tension of liquid Ar near the triple point

The effect of the transition zone on the surface energy and the surface tension near the triple point is reported. Both quantities are calculated from the extended Kirkwood-Buff formulas for the cases of a linear, a cubic, and a Fermi density profile. The realistic Barker-Fisher-Watts (BFW) potential and the Parson, Siska, and Lee (MSVIII) potential are used. The experimental radial distribution function of Yarnell et al. is used for the bulk liquid and as an approximation for the transition zone. As a function of the zone width both realistic potentials lead to the same rapid monotonic increase for the surface energy, but a different mild monotonic decrease for the surface tension. The transition zone width can be determined approximately from the surface energy. If the three-body nonadditivity effects on both quantities are ignored, the experimental value 34.9 erg/${\mathrm{cm}}^2$ of the surface energy suggests a zone width of 6.2 to 8.5 Å, thus predicting a value of the tension of 12.1 dyn/cm for the BFW potential and 12.8 dyn/cm for the MSVIII potential as compared to the experimental value of 13.1 dyn/cm. Including the three-body nonadditivity effects estimated from the Axilrod-Teller triple-dipole potential, the zone width needed for a correct value of the surface energy is slightly larger (7.2 to 9.5 Å). However, the surface tension thus predicted is too small for all potentials.