Geometries and electronic structures of the hydrogenated diamond （100） surface upon exposure to active ions： A first principles study

To elucidate the effects of physisorbed active ions on the geometries and electronic structures of hydrogenated diamond films, models of HCO3, H3O^＋, and OH^- ions physisorbed on hydrogenated diamond （100） surfaces were constructed. Density functional theory was used to calculate the geometries, adsorption energies, and partial density of states. The results showed that the geometries of the hydrogenated diamond （100） surfaces all changed to different degrees after ion adsorption. Among them, the H3O^＋ ion affected the geometry of the hydrogenated diamond （100） surfaces the most. This is well consistent with the results of the calculated adsorption energies, which indicated that a strong electrostatic attraction occurs between the hydrogenated diamond （100） surface and H3O^＋ ions. In addition, electrons transfer significantly from the hydrogenated diamond （100） surface to the adsorbed H3O^＋ ion, which induces a downward shift in the HOMO and LUMO energy levels of the H3O^＋ ion. However, for active ions like OH^- and HCO3^, no dramatic change appears for the electronic structures of the adsorbed ions.