First-Principles Study on Cation-Antisite Defects of Stannate and Titanate Pyrochlores

摘要

The structure and formation energies of cation antisite defects for a series of stannate pyrochlores A2Sn2O7 (A = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Lu, and Y) and titanate pyrochlores A2Ti2O7 (A = La, Sm, Gd, Tb, Dy, Ho, Er, Lu, and Y) have been systematically investigated using the first-principles total energy calculations. The calculated results reveal that the lattice parameters increase and the oxygen positional parameters decrease with increasing ionic radii of the lanthanides in the stannate and titanate pyrochlore compounds, respectively. The results suggest that cation antisite defects in pyrochlore play an important role in determining their radiation-resistant properties. The present studies indicate formation energies of cation antisite defects are not simple functions of ionic radius, radius ratio, lattice parameters, and the oxygen positional parameters.