Ab initiostudy of Cu diffusion inα-cristobalite

M Zelený, J Hegedüs, A S Foster, D A Drabold, S R Elliott, R M Nieminen
2012 New Journal of Physics  
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
more » ... g 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 transitionstate 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.
doi:10.1088/1367-2630/14/11/113029 fatcat:kp4gfyzlenckvelkutneanxyse