The Model of Ferroelectricity in Thiourea

In this paper we propose a mechanism of the phenomenon of ferroelectricity in the molecular crystal of thiourea $(SC(NH_2)_2)$. The mechanism is based on the model of interaction between two molecular electric dipoles. The dipoles are not idealized to points - they have a finite length. Besides, they can reorient mutually and the reorientation is determined by the crystal structure specified by the experimental structural research. On the basis of this theory, a formula for the potential energy of interaction of a pair of two nonpunctual dipoles as a function of the angle of reorientation is derived and discussed.