The determination of contact angle of water on graphite surface: Using grand canonical transition matrix Monte Carlo
Choong, Wai Keong
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Grand canonical transition matrix Monte Carlo simulation is used to investigate the wetting phenomena of water on graphite surfaces. The water model is chosen to be SPC/E. This new simulation technique directly evaluates the spreading coefficient, from which the contact angle and solid-liquid and solid-vapor interfacial tensions are deduced. We examine these properties as a function of temperature (300-550K) and wall strength (0.3135-0.60 kJ/mol). Results from the simulation are compared with the work of Werder [J. Phys. Chem. B 107, 1345 (2003)] in which molecular dynamics (MD) simulation was used to determine the contact angle of water droplets. Our results indicate that the system exhibits nonwetting behavior for a wall strength of 0.3135kJ/mol, where contact angles Θ are found in the range of 100°-107°. Wetting transitions are observed at higher substrate strengths. We observe wetting transitions for wall strengths greater than 0.4389kJ/mol, with wetting transition temperatures in the range of 400-530K. Finally, different system sizes are examined, with our results indicating that system size has a negligible influence on interfacial properties.