Order-disorder structure of triglycine sulfate under electric field

Crystal structures of triglycine sulfate single crystals under DC and AC electric fields have been analyzed in the ferroelectric phase by X-ray diffraction. Ratio between positive domains and negative domains in the sample can be confirmed by Flack's parameter considered the X-ray anomalous dispersion effect. Atomic positions in the unit cell of both parallel and anti-parallel dipole configurations can be determined simultaneously with the split-atom method. Displacement of sulfur atom with polarization reversal turns out to be 0.14 Å. Existence ratio between these two configurations can be derived from atom occupancy probability. Long range order parameter at room temperature is estimated to be about 0.78.