M CENTER DIFFUSION, EXCITONS AND ADSORPTIVITY OF ATOMIC H AND HeON LiH (001) SURFACE: ab initioSTUDY

A. S. Shalabi (), Kh. M. Eid, M. A. Kamel and Z. M. Fathi
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A. S. Shalabi: Department of Chemistry, Faculty of Science, Benha University, Benha, Egypt
Kh. M. Eid: Department of Physics, Faculty of Education, Ain Shams University, Cairo, Egypt
M. A. Kamel: Department of Physics, Faculty of Education, Ain Shams University, Cairo, Egypt
Z. M. Fathi: Department of Physics, Faculty of Education, Ain Shams University, Cairo, Egypt

International Journal of Modern Physics C (IJMPC), 2000, vol. 11, issue 08, 1491-1507

Abstract: An attempt has been made to examine the energetic properties of M center diffusion, excitons nearM2+,M+, M,M-andM2-centers and adsorptivity of atomic H and He over defect free and defect containing surfaces of LiH using anab initioembedded cluster method at the Hatrtree–Fock approximation and Moller–Plesset second order perturbation correction. The results confirm the following, (1) the calculated barriers to diffusion of M center in its lowest triplet excited state is always greater than those in its singlet ground state; (2) the triplet M center is not produced directly by optical processes, but, indirectly by thermal diffusion; (3) the exclusive dependence of exciton bands and the nonexclusive dependence of band gaps on the defect charge; (4) surface relaxation is not more important than bulk relaxation; (5) the M center changes the nature of H adsorption from physical adsorption to chemical adsorption; (6) bulk or surfaceM2-changes the nature of LiH from an insulator to a semiconductor; (7) as M center is introduced, the HOMO and LUMO levels of the substrate shift to higher energies and band gaps become narrower. This change in the electronic structure makes charge transfer between adsorbate and substrate levels and spin pairing with atomic H more facile.

Keywords: M center; Bulk; Surface; Excitons; Adsorption; LiH; ab initio; Singlet–Triplet Crossing (search for similar items in EconPapers)
Date: 2000
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DOI: 10.1142/S0129183100001498

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