Dynamics of the hydride ion in MgO single crystals
Autor(en): | Monge, M.A. González, R. Popov, A.I. Pareja, R. Chen, Y. Kotomin, E.A. Kuklja, M.M. |
Stichwörter: | Absorption spectroscopy; Activation energy; Annealing; Computer simulation; Hydrides; Hydrogen; Infrared spectroscopy; Magnesia; Mathematical models; Negative ions; Point defects; Single crystals; Diffusion; Ions; Isothermal annealing; Light absorption; Magnesia; Molecular physics; Quantum chemistry; Single crystals, Hartree-Fock cluster method; Interstitials; Vacancies, Diffusion in solids; Activation energy, Ab - initio Hartree-Fock; Elevated temperature; Experimental values; First-order kinetic reaction; Hartree-fock; MgO single crystals; Theoretical modeling; Thermo-chemically | Erscheinungsdatum: | 1999 | Herausgeber: | Scitec Publications Ltd., Zurich, Switzerland | Journal: | Diffusion and Defect Data. Pt A Defect and Diffusion Forum | Volumen: | 169 | Startseite: | 1 | Seitenende: | 11 | Zusammenfassung: | Diffusion of H- ions in thermochemically reduced MgO crystals with a large concentration of hydrogen has been investigated both experimentally and theoretically. Infrared absorption of the [H-]+ centers is used to monitor the concentration and to study their diffusion rates in crystals heated at elevated temperatures in flowing oxygen. Characteristics parameters such as activation energy and diffusion coefficients were determined. The diffusion coefficient is ≈10-6 cm2/s at 1600 K. The activation energy is estimated experimentally to be (1.5±0.3) eV. Analysis of the decay curves of [H-]+ center concentrations during isothermal anneals indicates that the annealing-out of the [H-]+ centers does not follow a first-order kinetic reaction. The H- ion diffusion was simulated using an ab-initio Hartree-Fock cluster approach. The mobile defect is more compatible with the H- ion than with the proton. Theoretical modeling for the direct interstitial H- hops along the [100] axis gives an activation energy twice as large as the experimental value. It is proposed that either a collinear interstitialcy mechanism for diffusion, or motion of the H--oxygen vacancy complex are involved. |
ISSN: | 10120386 | Externe URL: | https://www.scopus.com/inward/record.uri?eid=2-s2.0-0344339124&partnerID=40&md5=397102a6ff4bd291ffd6c93a795607d7 |
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