Threshold displacement energies and defect formation energies inY2Ti2O7

Abstract

Ab initio molecular dynamics simulations have been carried out to determine both threshold displacementenergies, Ed, and corresponding defect configurations, and ab initio methodshave been used to determine defect formation energies inY2Ti2O7. Theminimum Ed is found to be 27 eV for a Y recoil along the⟨100⟩ direction, 31.5 eV forTi atoms along the ⟨100⟩ direction, 14.5 eV for O48f atoms along the ⟨110⟩ direction and 13 eV for O8b atoms along the ⟨111⟩ direction. The average Ed values along three directions determined here are 35.1, 35.4, 17.0 and 16.2 eV for yttrium, titanium,O48f andO8b atoms, respectively. Cation interstitials are observed occupying vacant 8aanion sites and bridge sites between two neighboring cations along the⟨010⟩ direction after low energy recoil events. A systematic study of the defect formation energiessuggests 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 cationinterstitials may provide a pathway for driving irradiation induced amorphization inY2Ti2O7.