Threshold displacement energies and defect formation energies in Y2Ti2O7.

Ab initio molecular dynamics simulations have been carried out to determine both threshold displacement energies, E(d), and corresponding defect configurations, and ab initio methods have been used to determine defect formation energies in Y(2)Ti(2)O(7). The minimum E(d) is found to be 27 eV for a Y recoil along the {100} direction, 31.5 eV for Ti atoms along the {100} direction, 14.5 eV for O(48f) atoms along the {110} direction and 13 eV for O(8b) atoms along the {111} direction. The average E(d) values along three directions determined here are 35.1, 35.4, 17.0 and 16.2 eV for yttrium, titanium, O(48f) and O(8b) atoms, respectively. Cation interstitials are observed occupying vacant 8a anion sites and bridge sites between two neighboring cations along the {010} direction after low energy recoil events. A systematic study of the defect formation energies suggests that cation interstitials that are located at 8a sites, at bridge sites along the {010} direction and in split configurations along the {010}, {110} or {111} direction are all stable configurations. It is suggested that the relative stability of cation interstitials may provide a pathway for driving irradiation induced amorphization in Y(2)Ti(2)O(7).