Please use this identifier to cite or link to this item: http://hdl.handle.net/10995/27190
Title: Investigation of cation self-diffusion mechanisms in UO 2±x using molecular dynamics
Authors: Boyarchenkov, A. S.
Potashnikov, S. I.
Nekrasov, K. A.
Kupryazhkin, A. Ya.
Issue Date: 2013
Citation: Investigation of cation self-diffusion mechanisms in UO 2±x using molecular dynamics / A. S. Boyarchenkov, S. I. Potashnikov, K. A. Nekrasov [et al.] // Journal of Nuclear Materials. — 2013. — Vol. 442. — № 1-3. — P. 148-161.
Abstract: This article is devoted to investigation of cation self-diffusion mechanisms, taking place in UO2, UO2+x, and UO2-x crystals simulated under periodic (PBC) and isolated (IBC) boundary conditions using the method of molecular dynamics in the approximation of rigid ions and pair interactions. It is shown that under PBC the cations diffuse via an exchange mechanism (with the formation of Frenkel defects) with activation energy of 15-22 eV, while under IBC there is competition between the exchange and vacancy (via Schottky defects) diffusion mechanisms, which give the effective activation energy of 11-13 eV near the melting temperature of the simulated UO2.00 nanocrystals. Vacancy diffusion with lower activation energy of 6-7 eV was dominant in the non-stoichiometric crystals UO2.10, UO2.15 and UO 1.85. Observations showed that a cation vacancy is accompanied by different number of anion vacancies depending on the deviation from stoichiometry: no vacancies in UO2.15, single vacancy in UO 2.00 and four vacancies in UO1.85. The corresponding law of mass action formulas derived within the Lidiard-Matzke model allowed explaining the obtained activation energies and predicting a change in the activation energy within the temperature range of the superionic phase transition. The diffusion of cations on the surface of nanocrystals had activation energy of 3.1-3.6 eV. © 2013 Elsevier Ltd. All rights reserved.
Keywords: DIFFUSION MECHANISMS
EFFECTIVE ACTIVATION ENERGY
EXCHANGE MECHANISM
LAW OF MASS ACTION
NON-STOICHIOMETRIC
SUPERIONIC PHASE TRANSITION
TEMPERATURE RANGE
VACANCY DIFFUSION
DIFFUSION
MOLECULAR DYNAMICS
NANOCRYSTALS
POSITIVE IONS
VACANCIES
ACTIVATION ENERGY
URI: http://hdl.handle.net/10995/27190
SCOPUS ID: 84884586184
WOS ID: WOS:000328175400019
PURE ID: 861700
ISSN: 0022-3115
DOI: 10.1016/j.jnucmat.2013.08.030
Appears in Collections:Научные публикации, проиндексированные в SCOPUS и WoS CC

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