First-principles study of the incorporation and diffusion of helium in cubic zirconia

TL;DR

This study uses first-principles calculations to explore how helium incorporates and diffuses in cubic zirconia, revealing preferred sites, diffusion mechanisms, and consistency with experimental data.

Contribution

It provides detailed insights into helium behavior in cubic ZrO₂, including defect formation energies and diffusion pathways, which were not previously well understood.

Findings

He prefers Zr vacancies for incorporation

He diffuses mainly via vacancy-assisted hopping

Calculated diffusion energies match experimental results

Abstract

The incorporation and diffusion of helium (He) with and without intrinsic vacancy defects in cubic ZrO$_{2}$ are investigated through first-principles total-energy calculations, in which the projector-augmented-wave (PAW) method with the generalized gradient approximation (GGA) is used. The calculated formation energies of intrinsic point defects indicate that cubic ZrO$_{2}$ has a tolerant resistance to radiation damage. The incorporation energy of He impurity shows that it is preferable to occupy the Zr vacancy at first, whereas the solution energy suggests that He would be accommodated in the interstitial site at thermodynamic equilibrium concentration. By calculating the He migration energies corresponding to both interstitial and vacancy assisted mechanisms, we suggest that it is most likely for He to diffuse by hopping through a single vacancy. Remarkably, our calculated vacancy-assisted diffusion energy of He is consistent well with the experimental measurement.