Why h atom prefers the on-top site and alkali metals favor the middle hollow site on the Basal plane of graphite

J Phys Chem B. 2005 Apr 28;109(16):7923-7. doi: 10.1021/jp044407s.

Abstract

In this work, the different adsorption properties of H and alkali metal atoms on the basal plane of graphite are studied and compared using a density functional method on the same model chemistry level. The results show that H prefers the "on-top site" while alkali metals favor the "middle hollow site" of graphite basal plane due to the unique electronic structures of H, alkali metals, and graphite. H has a higher electronegativity than carbon, preferring to form a covalent bond with C atoms, whereas alkaline metals have lower electronegativity, tending to adsorb on the highest electrostatic potential sites. During adsorption, there are more charges transferred from alkali metal to graphite than from H to graphite.