Ab Initio Molecular Dynamics Study of Alignment-Resolved O2 Scattering from Highly Oriented Pyrolytic Graphite

Abstract

We present ab initio molecular dynamics simulations based on density functional theory to study the alignment dependent scattering of O2 from highly oriented pyrolytic graphite (HOPG). Results are obtained for 200 meV O2 molecules with different alignments impinging with an angle of incidence measured from surface normal of 22.5○ on a thermalized (110 and 300 K) graphite surface. The choice of these initial conditions in our simulations is made in order to perform comparisons with recent experimental results on this system. Our results show that a lower number of molecules initially aligned normal to the surface is reflected in the scattering plane than of molecules initially aligned parallel to the surface. This is not due to an increase of the trapping of end-on aligned molecules, but due to the fact that a large amount of them are scattered out of plane. Additionally, we find that the final translational energy of end-on molecules is around 10 % lower than that of side-on molecules. We show that this i...