Potential functions of ions in cubic BaTiO3

Integrated intensities of X-ray Bragg reflections (Ag-Kα radiation) from barium titanate single crystal were measured as a function of temperature above the Curie point of 131.20C. The harmonic and fourth order anharmonic potential parameters for constituent ions were estimated from the thermal vibration amplitude of each ion. Potential parameters are: α(Ba) = 1.018 x 10-11 erg A-2, α(Ti) = 0.730 x 10-11 erg A-2, α(O) = 0.265 x 10-11 erg A-2, α'(O) = 0.999 x 10-11 erg A-2, γ(Ba) = 0.055 x 10-11 erg A-4, γ(Ti) = 0.679 x 10-11 erg A-4, γ(O) = -0.400 x 10-11 erg A-4, γ'(O) = 2.99 x 10-11 erg A-4; and the Grueneisen constant is 1.22. These values are consistent with suggestions presented in previous neutron diffraction studies by Y. Yamada et al. and J. Harada et al. (author)