THERMAL VIBRATIONS IN PBTIO3 CRYSTALS

The thermal vibration amplitudes were studied in high temperature para electric phase of PbTiO3 crystals. The values of amplitudes were compu ted first assuming the positions of Pb and Ti ions given by Pm3m space group and then allowing the possibility of random displacements from these positions. Assumption of the random displacements gives essentia l results only for ph ions. Therefore the thermal vibrations of Pb rat her than Ti ions implicate a disorder in PbTiO3 paraelectric phase.