A Point Charge Model for the Ferroelectric Transition in Ammonium Sulphate

Abstract

Abstract In ammonium sulphate the distortion of the SO 4 2− ion, which has almost tetrahedral symmetry in its paraelectric phase, occurs in a narrow region near the ferroelectric transition temperature T c = 223 °K. A point charge model has been used to compute the spontaneous polarization ( P ) due to NH and SO ions in the crystal. The computed value of P (0.42 μC/cm 2 ) agrees well with the experimentally reported ones. The nature of phase transition has also been discussed.