On the Water−Carbon Interaction for Use in Molecular Dynamics Simulations of Graphite and Carbon Nanotubes

A systematic molecular dynamics study shows that the contact angle of a water droplet on graphite changes significantly as a function of the water−carbon interaction energy. Together with the observation that a linear relationship can be established between the contact angle and the water monomer binding energy on graphite, a new route to calibrate interaction potential parameters is presented. Through a variation of the droplet size in the range from 1000 to 17 500 water molecules, we determine the line tension to be positive and on the order of 2 × 10 -10 J/m. To recover a macroscopic contact angle of 86°, a water monomer binding energy of −6.33 kJ mol -1 is required, which is obtained by applying a carbon−oxygen Lennard-Jones potential with the parameters ε CO = 0.392 kJ mol -1 and σ CO = 3.19 Å. For this new water−carbon interaction potential, we present density profiles and hydrogen bond distributions for a water droplet on graphite.