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

TLDR

The study proposes a new calibration route for water–carbon interaction potentials by linking the contact angle of water on graphite to the monomer binding energy. Using systematic molecular dynamics simulations of water droplets ranging from 1,000 to 17,500 molecules on graphite, the authors established a linear relationship between contact angle and binding energy and derived Lennard–Jones parameters εCO = 0.392 kJ mol⁻¹ and σCO = 3.19 Å. They found that the contact angle varies with interaction energy, the line tension is positive (~2 × 10⁻¹⁰ J m⁻¹), and a binding energy of –6.33 kJ mol⁻¹ reproduces an 86° macroscopic contact angle, with accompanying density profiles and hydrogen‑bond distributions presented.

Abstract

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 εCO = 0.392 kJ mol-1 and σCO = 3.19 Å. For this new water−carbon interaction potential, we present density profiles and hydrogen bond distributions for a water droplet on graphite.