Computational studies of the structure of carbon dioxide monolayers physisorbed on the basal plane of graphite

Abstract

The molecular-dynamics method has been used to study carbon dioxide physisorbed on the basal plane of graphite at temperatures between 100 and 130K at monolayer and submonolayer coverages. Additionally, energy-minimization calculations have been used to explore the relative stability of a number of solid structures of the adsorbate. Three models of carbon dioxide, which have been successful in describing the properties of the bulk phase, where tested in these simulations of the adsorbate. The results at submonolayer coverage suggest that the adsorbate forms a two-sublattice incommensurate herringbone structure. These solid patches have approximately the correct melting point. At monolayer coverage the existence of a four-sublattice pinwheel structure was only observed for a model with an artificially enhanced quadrupole moment. Further refinement of the potential model will require additional calorimetric or diffraction experiments.