الفهرس 
Aim of studyOnly 14 pages are availabe for public view
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Abstract
The following major conclusions may be drawn from the analysis of the self-trapped hole (STH) centers:
(i) The ”on-center” configuration of the doublet ground configuration of STH is energetically more favored than the ”off-center” configuration with correlated activation energies barriers are 0.36 and 0.25 eV for bulk and surface diffusion. The positive hole is localized along the <llO> axis mainly at the anion vacancy sites and partially at the center of mass of the molecular ion. The self-trapped hole 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 self trapped hole 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.
(ii) The LiF and NaH isoelectronic clusters in crystals were found to exhibit distinct differences in the energetic properties. The off-center configuration of STH in the bulk of LiF was more stable than the on center configuration. The on-center configuration in the bulk of NaH was more stable than the off- center configuration. The activation barriers were calculated to be 0.07 and 0.30 eV for bulk and surface diffusion of STH in LiF respectively, and 0.66 and 0.60 eV for