Insights into the radiation behavior of Ln2TiO5 (Ln = La-Y) from defect energetics

Abstract

First-principles calculations have been performed to study the structural properties and defect energetics of orthorhombic Ln2TiO5 (Ln=La, Pr, Nd, Sm, Gd, Dy and Y). The lattice parameters decrease with increasing lanthanide cation radius. The mean 〈Ln1-O〉 and 〈Ln2-O〉 bond lengths increase systematically by respectively 1.16% and 1.19% from Dy2TiO5 to La2TiO5. Meanwhile, mean 〈Ti-O〉 bond length increases slightly with increasing Ln cation radius from Y2TiO5 to La2TiO5. The calculated results of point defect formation energies suggest that Ln2-Ti antisite defect is the most energetically favorable defect type for Ln2TiO5. The trend of Ln2-Ti antisite defect formation energy of Ln2TiO5 is precisely consistent with the radiation resistance, as demonstrates by the critical amorphization temperature, which indicates that the formation of Ln2-Ti antisite defect may has a significant influence on the radiation behavior of Ln2TiO5.