Classical dynamics study of atomic oxygen over graphite (0001) with new interpolated and analytical potential energy surfaces

Abstract

Two adiabatic potential energy surfaces (PESs) based on density functional theory data are constructed for the interaction of atomic oxygen with graphite (0 0 0 1) surface: an analytical FPLEPS PES and an interpolated Modified Shepard one. A classical trajectory study has been performed for the two PESs for different initial conditions: collision energy (0.1 ⩽ Ecol ⩽ 1.3 eV), surface temperature (100 ⩽ Tsurf ⩽ 900 K) and two incident angles (θv = 0°, 45°), and also for thermal conditions (T = TOxygen = Tsurf = 300-1500 K). In addition, hyperthermal experimental conditions corresponding to a hot atom distribution (〈Ecol〉 = 5.2 eV) were also considered. All the properties studied for the two PESs were in close agreement in almost the major part of the explored conditions, although some differences were obtained for low Ecol due to the presence of a physisorption minimum in the MS PES that was not included into the FPLEPS one. The adsorption process occurs mainly over bridge sites. Adsorption probabilities are lower than reflection ones in practically all the conditions explored and increase quickly with Ecol until a maximum and then decrease smoothly. Polar scattering angle distributions present a peak centred around the specular angle position and broaden when increasing Ecol or Tsurf. A good agreement respect this peak position was found in comparison with the experimental hyperthermal data. The transfer of energy is mainly from the atom to the surface and increases when initial collision energy does.