Development and application of the modified strong dipole-proton coupling model for KDP-type crystals

The modified strong dipole-proton coupling (MSDPC) model, which predicted several static and dynamic dielectric properties of KDP-type ferroelectrics, was used to investigate local properties of these crystals. The results showed both order-disorder and displacive characteristics of pure KDP and DKDP, as in many other experimental studies (NMR, neutron scattering) of local properties. Paramagnetic center SeO4 introduced in KDP and DKDP lattice as a local probe in EPR technique was treated within MSDPC model as a “soft” impurity. Simulated dipole reorientational dynamics of the impurity showed characteristics similar to the slow local dynamics of the probe detected in an EPR experiment. Additionally, the MSDPC model was adapted to describe dielectric properties of KDP-type antiferroelectrics. Antiferroelectric phase transition of the first order and isotopic shift in Tc were reproduced.