COMPUTER-SIMULATION OF CRYSTAL-LIQUID INTERFACE - APPLICATION TO WETTABILITY OF SOLIDS

Purpose. This study describes the development and application of a mol ecular simulation technique for investigating the solid-liquid interfa ce. It attempts to relate the molecular and crystal structure to the o bserved wettability of solids. Method Molecular simulations have been carried out for the crystal-water interface of a series of N-n-alkyl-D -gluconamide crystals using the Monte Carlo technique. The molecular s ystem simulated consisted of a layer of water bounded by two crystal s labs. The interfacial potential energies were calculated for the cryst al-water interactions and compared with experimental enthalpy values o btained from contact angle measurements. Results. The simulations clea rly reveal the distinct hydrophilic and hydrophobic nature of the resp ective (010) and (0(1) over bar0$) faces of these compounds. The distr ibution of water at the interface observed in the simulations is in ac cord with the nature of the crystal faces. The calculated interfacial potential energies are in the right ball park, but consistently higher than the experimental values. The disparity, however, is justifiable, resulting from the highly simplified model simulated. Conclusions. Us ing the developed molecular simulation technique one can calculate the wettability of a solid given the crystal structure. This approach rep resents an important step towards the goal of engineering crystals wit h desired wettability characteristics.