Mechanism for electro-optic effect in BaTiO3

An ab initio calculation method has been used to check the theoretical model given by the paper [1]. The result shows that the origin of electro-optic effect in the BaTiO
3
crystal come certainly from the relative displacements of the Ti
⁴⁺
to the oxygen ions in the octahedron (TiO
6
) group, and then the displacements of Ti
⁴⁺
lead to the changes of the band wave function of electrons in the crystal which produce the changes of refractive indices no and ne in the crystal. The calculations further point out that the rate Δn
i
/Δl
k
is almost proportionate to the parameter β
k
(i).