In orderr to elucidate the oxygen vacancies effects on La3Ta0.5Ga5.5O14, formation energy of each electronic state of oxygen vacancies (VO••, VO• and VOx) at non-equivalent Wyckoff positions (2d and 6g) and their electronic structures were calculated by combining GW quasi-particle scheme and conventional density functional theory. The formation energy of VO(6g) was lower than the formation energy of VO(2d) in each electronic state. Thus, relatively stable oxygen vacancies at 6g sites (VO(6g)) could be major oxygen vacancies in this system. Also, the calculated band-gaps of La3Ta0.5Ga5.5O14 with thermodynamically stable defects such as VO(6g)•• or VO(6g)x were higher than band gaps of La3Ta0.5Ga5.5O14 with VO(2d)•• or VO(2d)x at the Γ-point. By the band interpolation based on Boltzmann transport theory, calculated electrical conductivities per unit relaxation time (σ/τ) of the LTG with VO(2d)•• and VO(6g)•• were similar at the same electron energy, however, σ/τ of the LTG with VO(2d)x was higher than that of the LTG with VO(6g)x.

GW Calculations on La3Ta0.5Ga5.5O14 with Oxygen Vacancies at Non-Equivalent Sites. C.Y.Chung, R.Yaokawa, H.Mizuseki, Y.Kawazoe: Computational Materials Science, 2012, 54, 43–7