First-principles calculation of defect formation energies and electronic properties in stannate pyrochlores

Abstract

The electronic structures and defect formation energies for a series of stannate pyrochlores Ln2Sn2O7 (Ln=La, Pr, Nd, Sm, Gd, Tb, Ho, Er, Lu, and Y) have been investigated using the first-principles total energy calculations. The calculated results show that Ln-site cation ionic radius, x-O48f, lattice constant and the covalency of the ⟨Sn–O48f⟩ bond have a significant affect on the defect formation energies. The cation-antisite defect has the lowest formation energy, as compared with that of other defects, indicating that cation disorder causes local oxygen disordering. The present studies suggest that Lu2Sn2O7 is the most resistant to ion beam-induced amorphization. The electronic structure calculations reveal that Ln2Sn2O7 compounds have direct band gaps of 2.64–2.95 eV at the Γ point in the Brillouin zone.