First principles studies for the interaction of hydrogen with a Li(100) surface

We investigate the interaction of molecular/atomic hydrogen with the Li surface. We calculate the potential energy surfaces (PESs) for H-2 and the potential energy curves (PECs) for H at symmetric sites on a Li(100) surface within the density functional theory. The PESs results show the dependence of the energy barriers for H-2 dissociative adsorption and the stable adsorption sites for the dissociated H atoms on the H-2 center-of-mass (CM) position and the H-2 orientation relative to the surface. Also, reaction paths for the direct absorption of H-2 can be seen when the H-2 CM is directly above the bridge site of the Li(100) surface. Meanwhile, the PECs results indicate that the energy barriers for H absorption and the stable H adsorption sites depend on the H lateral position relative to the surface. A very low energy barrier was observed for H absorption on the bridge site of the surface. Finally, we present a practical explanation of the PESs' and PECs' dependence on the H-2 position and orientation relative to the surface from the interaction between the electrons of hydrogen and of the substrate atoms, as well as from the lattice structure of the substrate.