O ct 2 00 4 NaCl nanodroplet on NaCl ( 100 ) at the melting point

The self-wetting properties of ionic crystal surfaces are studied, using NaCl(100) as a prototype case. The anomalously large contact angle measured long ago by Mutaftschiev [1,2] is well reproduced by realistic molecular dynamics simulations. Based on these results, and on independent determinations of the liquid-vapor (γ LV) and the solid-vapor interface free energy (γ SV) [3], an estimate of the solid-liquid interface free energy (γ SL) 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.