Reorientation of self-trapped hole and adsorptivity of atomic hydrogen on LiH (001) surface: ab initio study Original Research Article

An ab initio embedded molecular cluster method was used to examine the bulk and surface orientations of the self-trapped hole (STH), activation barriers for diffusion of STH along the 〈110〉 axis and the effect of STH on the adsorptivity and mobility of atomic H over the surface using the Hartree–Fock approximation and Moller–Plesset second order perturbation correction. The “on-center” configuration of the doublet ground state is energetically more favored than the “off-center” configuration and the correlated activation barriers are 0.36 and 0.25 eV for bulk and surface diffusion. The positive hole is localized along the 〈110〉 axis mainly at the anion vacancy sites and partially at the center of mass of the molecular ion. The STH enhances the adsorptivity of atomic hydrogen by ∼3.5 eV at the correlated level, changes the nature of adsorption from physisorption to chemisorption and restricts the mobility of atomic H over the surface. As the STH is introduced to the crystal surface, the HOMO and LUMO levels shift to lower energies and the valence-conduction band gap broadens. This change in the electronic structure makes spin pairing between adsorbate singly occupied atomic orbital and substrate singly occupied molecular orbital more facile in the course of adsorbate–substrate interactions.