### 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 SiO_{2} 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 SiO _{2}, 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.

Original language | English |
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Article number | 113029 |

Pages (from-to) | 1-21 |

Number of pages | 21 |

Journal | New Journal of Physics |

Volume | 14 |

Issue number | November |

DOIs | |

Publication status | Published - Nov 2012 |

MoE publication type | A1 Journal article-refereed |

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## Cite this

*New Journal of Physics*,

*14*(November), 1-21. [113029]. https://doi.org/10.1088/1367-2630/14/11/113029