[SY-B9] Ab Initio Modeling of Self-Interstitial and Vacancy Migration in Zirconium
Irradiation in hexagonal close-packed zirconium leads to the creation of point-defects, both vacancies and self-interstitials. Migration and clustering of these point-defects control the microstructure evolution under irradiation. In particular, the faster diffusion of self-interstitial in the basal planes than along the c axis is often assumed to explain the self-organization of the microstructure observed in irradiated Zr as well as the breakaway growth visible for high irradiation dose. As no direct experimental measurement characterizing a possible diffusion anisotropy is possible, at least for the self-interstitial, ab-initio calculations appear as a suitable alternative.
We model with ab initio calculations all possible configurations of the self interstitial and calculat with NEB the different migration barriers between these configurations [1]. The attempt frequencies corresponding to the different migration events are deduced from phonon calculations thanks to the harmonic approximation and the transition state theory. We thus fully characterize the migration of both the self-interstitial and the vacancy. The obtained ab initio data is validated by modeling internal friction in irradiated zirconium and comparing the low temperature peaks with the ones observed in experiments [2]. Once this validation step performed, diffusion coefficients are calculated and diffusion anisotropy is characterized.
[1] C. Varvenne, F. Bruneval, M.-C. Marinica and E. Clouet, Phys. Rev. B 88, 134102 (2013).
[2] R. Pichon, E. Bisogni and P. Moser, Radiation Effects 20, p. 159 (1973).
We model with ab initio calculations all possible configurations of the self interstitial and calculat with NEB the different migration barriers between these configurations [1]. The attempt frequencies corresponding to the different migration events are deduced from phonon calculations thanks to the harmonic approximation and the transition state theory. We thus fully characterize the migration of both the self-interstitial and the vacancy. The obtained ab initio data is validated by modeling internal friction in irradiated zirconium and comparing the low temperature peaks with the ones observed in experiments [2]. Once this validation step performed, diffusion coefficients are calculated and diffusion anisotropy is characterized.
[1] C. Varvenne, F. Bruneval, M.-C. Marinica and E. Clouet, Phys. Rev. B 88, 134102 (2013).
[2] R. Pichon, E. Bisogni and P. Moser, Radiation Effects 20, p. 159 (1973).