Water-carbon interactions III: The influence of surface and fluid impurities

Molecular dynamics. simulations are performed to study the influence of surface and fluid impurities on water-carbon interactions. In order to quantify these interactions we consider the canonical problem of wetting of a doped flat graphitic surface by a water system with impurities. As model fluid impurities we consider aqueous solutions of potassium-chloride with molar concentrations up to 1.8 M. Quantum chemistry calculations are performed to derive pair potentials for the ion-graphite interactions. The contact angle is found to decrease weakly with increasing ionic concentration, from 90degrees at 0 M to 81degrees at 1.8 M concentration. The influence of solid impurities is found to be more significant. Thus, 10, 15, and 20% coverages of chemisorbed hydrogen result in contact angles of 90degrees, 74degrees and 60degrees, respectively.