Ab initio molecular dynamics simulations of ion–solid interactions in Gd2Zr2O7 and Gd2Ti2O7

Abstract

The development of the ab initio molecular dynamics (AIMD) method has made it a powerful tool in describing ion–solid interactions in materials, with the determination of threshold displacement energies with ab initio accuracy, and prediction of a new mechanism for defect generation and new defective states that are different from classical molecular dynamics (MD) simulations. In the present work, this method is employed to study the low energy recoil events in Gd₂Zr₂O₇ and Gd₂Ti₂O₇. The weighted average threshold displacement energies in Gd₂Zr₂O₇ are determined to be 38.8 eV for Gd, 41.4 eV for Zr, 18.6 eV for O_48f, and 15.6 eV for O_8b, which are smaller than the respective values of 41.8, >53.8, 22.6 and 16.2 eV in Gd₂Ti₂O₇. It reveals that all the ions in Gd₂Zr₂O₇ are more easily displaced than those in Gd₂Ti₂O₇, and anion order–disorder is more likely to be involved in the displacement events than cation disordering. The average charge transfer from the primary knock-on atom to its neighbors is estimated to be ∼0.15, ∼0.11 to 0.27 and ∼0.1 to 0.13 |e| for Gd, Zr (or Ti), and O, respectively. Neglecting the charge transfer in the interatomic potentials may result in the larger threshold displacement energies in classical MD.