Low energy ion-solid interactions and chemistry effects in a series of pyrochlores

The effect of chemistry on low energy recoil events was investigated at 10K for each type of atom in pyrochlores, using molecular dynamics simulation. Contour plots of the threshold displacement energy (E-d) in Gd2Zr2O7 have been produced along more than 80 directions for each individual species. The E-d surface for each type of atom in Gd2Zr2O7 is highly anisotropic; E-d of Zr exhibits the largest degree of anisotropy, while that of O-8b exhibits the smallest. The recommended values of E-d in Gd2Zr2O7 based on the observed minima are 56, 94 and 25 eV, respectively, for Gd, Zr, and O. The influence of cation radius on E-d in pyrochlores A(2)B(2)O(7) (with A-site ranging from Lu3+ to La3+ and B-site ranging from Ti4+ to Ce4+) was also investigated along three directions [100], [110], and [111]. The E-d in pyrochlores strongly depended on the atom type, atom mass, knock-on direction, and lattice position. The defects produced after low energy displacement events included cation antisite defects, cation Frenkel pairs, anion Frenkel pairs, various vacancies, and interstitials. Ce doping in pyrochlores may affect the radiation response, because it resulted in drastic changes in cation and anion displacement energies and formation of an unusual type of anti-site defect. This work demonstrates links between E-d and amorphization resistance.