Comparative study of friction properties for hydrogen- and fluorine-modified diamond surfaces: A first-principles investigation

The van der Waals corrected first-principles approach within density functional theory has been performed to calculate the interaction energies and friction coefficients for hydrogen- and fluorine-terminated diamond film systems. Comparative studies show that the fluorine-terminated diamond film is more stable and chemically inert than that of hydrogen termination. The repulsive interactions between two fluorine-terminated diamond films are stronger than that of hydrogen termination system, and the former system has a larger equilibrium adsorption heights than that of the latter. Quantitative calculations show that the hydrogen-terminated diamond film system has larger potential barriers and hence larger friction coefficients of about 0.15 under the loads of 0.5–3 nN, which are almost twice larger than that of fluorine-terminated system (about 0.08). The results are in good agreement with experiments and other theoretical predictions.