Studies of the local geometry for Fe3+ in LiTaO3 crystal from EPR data

The EPR zero-field splitting D for Fe3+ in LiTaO3 crystal has been calculat ed from the microscopic spin-orbit coupling mechanism and the empirical sup erposition model. It is found that to reach the good fit between the calcul ated and observed values of D, the Fe3+ ion does not occupy the exact Li+ s ite, but is required to move about 0.24 +/- 0.11 Angstrom in the direction of the -c axis in LiTaO3 crystal. The result is very similar to that for Fe 3+ in the isomorphous LiNbO3 crystal obtained from the X-ray standing waves experiment. The reasonableness-of the Fe3+ displacement is discussed.