Atomic-scale study of the nonmelting, wetting, and freezing behavior of KCl(100)

Abstract

The objective of this work is to study the thermodynamic properties of the KCl(100) surface by means of Molecular Dynamics (MD) simulation based on the Fumi-Tosi potential. The reliability of this potential model was tested to be quite accurate from the calculated bulk melting temperature ${T}_{m}$. The latter quantity was derived from the coexistence procedure of both solid and liquid states. After this preliminary study, the surface (100) of KCl was heated up to the bulk melting temperature and overheated until ${T}_{m}+243\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. As wetting and melting are thermodynamically linked, we have also investigated the wetting behavior from the calculation of the angular contact between a liquid nanodroplet and the nonmelting surface of KCl. Our simulation results give an angle of 47\ifmmode^\circ\else\textdegree\fi{} in fairly good agreement with the experimental data (49\ifmmode^\circ\else\textdegree\fi{}), which confirm the nonmelting behavior of the surface. It appears, however, that the thermodynamic way followed by the surface under the freezing process is not the same while heating. The calculated freezing temperature value corresponds to ${T}_{m}+215\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. This predictive phenomenon is explained by the important difference between the molar fraction of the liquid and the solid sates.