Origin Of Ferroelectric Phase Transition In Sboxs1-Xi Mixed Crystals

The dependence of the potential energy V(z) of Sb atoms on B-1u symmetry normal coordinates for SbOxS1-xI crystal in ferroelectric phase with a varying mixture x is investigated in the current paper. The potential energy of Sb atoms is characterized by a high anharmonicity within the temperature range 295-377 K. The large anharmonicity of the potential energy V (z) implies that SbOxS1-xI crystals exhibit intermediate behavior between displacement and order-disorder type phase transitions. The phase transition temperature T-C depends on the mixture composition x.