Based upon ab initio and classical molecular-dynamics simulations, an

investigation was made of the role played by vacancy-vacancy interactions in the

oxygen conductivity of yttria-stabilized and scandia-stabilized cubic zirconia. It

was found that an appreciable fraction of the possible configurations of vacancies

was locally unstable, although the vacancies were at least third-nearest neighbours

of each other. An investigation of the oxygen migration pathways by ab initio metadynamics simulations revealed the occurrence of multiple-vacancy concerted

jumps corresponding to an unstable arrival state for a single vacancy jump. In the

case of a single vacancy jump, a strong dependence of the activation barrier upon

the position of the other vacancies was observed; similar in strength to the

dependence of the activation energy upon the presence of nearest-neighbour

yttrium ions; usually to be a blocking site for vacancy migration. The results

indicated the need to improve existing models, of oxygen diffusion in stabilized

zirconium, by including vacancy-vacancy interactions.

Vacancy-Vacancy Interaction and Oxygen Diffusion in Stabilized Cubic ZrO2 from

First Principles. F.Pietrucci, M.Bernasconi, A.Laio, M.Parrinello: Physical Review

B, 2008, 78[9], 094301