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. (C) 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110:2231-2236, 2010