Polarizable ion model was used in describing the lattice dynamics in the Sn₂P₂S₆ and Sn₂P₂Se₆ ferroelectric crystals and their solid solutions. There has been obtained a good agreement of the calculated phonon spectra ...

Statistical theory for ferroelectrics based on triple well anharmonic potential was used for the case of structural second order phase transition in Sn₂P₂S₆ crystals. Parameters of effective Hamiltonian of the model ...