Ab initio study of Cu diffusion in alpha-cristobalite

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Journal Title
Journal ISSN
Volume Title
School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2012
Major/Subject
Mcode
Degree programme
Language
en
Pages
113029/1-21
Series
New Journal of Physics, Volume 14, Issue 11
Abstract
We have studied the geometries, formation energies, migration barriers and diffusion of a copper interstitial with different charge states with and without an external electric field in the α-cristobalite crystalline form of SiO2 using ab initio computer simulation. The most stable state almost throughout the band gap is charge q = + 1. The height of the migration barrier depends slightly on the charge state and varies between 0.11 and 0.18 eV. However, the charge has a strong influence on the shape of the barrier, as metastable states exist in the middle of the diffusion path for Cu with q = + 1. The heights and shapes of barriers also depend on the density of SiO2, because volume expansion has a similar effect to increase the positive charge on Cu. Furthermore, diffusion coefficients have been deduced from our calculations according to transition-state theory and these calculations confirm the experimental result that oxidation of Cu is a necessary condition for diffusion. Our molecular dynamics simulations show a similar ion diffusion, and dependence on charge state. These simulations also confirm the fact that diffusion of ions can be directly simulated using ab initio molecular dynamics.
Description
Keywords
ab initio computer simulation, copper interstitials, charge states
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Citation
Zelený, M. & Hegedüs, J. & Foster, Adam S. & Drabold, D. A. & Elliott, S.R. & Nieminen, R.M.. 2012. Ab initio study of Cu diffusion in alpha-cristobalite. New Journal of Physics. Volume 14, Issue 11. 113029/1-21. ISSN 1367-2630 (printed). DOI: 10.1088/1367-2630/14/11/113029