Interaction of atoms with graphenic‐type surfaces for the chemistry of the interstellar medium: New properties of H dimers on the surface

Following the works of Rougeau et al. (Chem Phys Lett 2006, 431,135) and Ferro et al. (Phys Rev B 2008, 78, 085417) on the one‐sided double chemisorption of H atoms on graphenic platelets, we investigate the two‐sided double chemisorption using DFT‐GGA PW91 calculations. Equilibrium characteristics and potential energy curves for chemisorption are reported for the ortho, meta, para, and bottom positions. Contrary to the one‐sided case, the two‐sided ortho chemisorption, as well as the bottom position, is barrier‐less, whereas the two‐sided para chemisorption exhibits an activation barrier. The highest occupied Kohn‐Sham orbital (HOKSO) of the H‐graphene radical is shown to signal the privileged barrier‐less double chemisorption sites.