NaCl nanodroplet on NaCl(1 0 0) at the melting point

The self-wetting properties of ionic crystal surfaces are studied, using NaCl(1 0 0) as a prototype case. The anomalously large contact angle measured long ago by Mutaftschiev [Surf. Sci. 47 (1975) 723; J. Cryst. Growth 182 (1997) 205] is well reproduced by realistic molecular dynamics simulations. Based on these results, and on independent determinations of the liquid–vapor (γLV) and the solid–vapor interface free energy (γSV) [Zykova-Timan et al. to be published], an estimate of the solid–liquid interface free energy (γSL) is extracted. The solid–vapor surface free energy turns out to be small and similar to the liquid–vapor one, providing a direct thermodynamic explanation of the reduced wetting ability of the ionic melt.