Ab initio study of Cu diffusion in alpha-cristobalite

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© 2012 IOP Publishing. This is the accepted version of the following article: 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, which has been published in final form at http://iopscience.iop.org/1367-2630/14/11/113029/. This work is distributed under the Creative Commons Attribution 3.0 License (https://creativecommons.org/licenses/by/3.0/)

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Journal ISSN

Volume Title

School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä

Date

2012

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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.

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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