FREE-ENERGY FUNCTIONS OF DISORDERED DIPOLE SYSTEMS

Free energy functions of disordered dipole systems i.e. dielectric cry stals with randomly situated impurity electric dipoles is derived. To derive free energy we used the supposition that action of other impuri ties to given one is represented by random local electric field. Our t heory is suitable for arbitrary dipole-dipole interaction potential an d rigorously takes into account the number of impurity dipole orientat ions in a host lattice (e.g. six orientations for Li+ in KTaO3 and eig ht for NB5+). Domain states in aforementioned systems are considered f or the first time. It is shown that the theory is in good coincidence with experimental situation in KTaO3:Li and Nb and new experiments are proposed.