Statistical theory of thermodynamic and dynamic properties of the RbHSO${}_4$ ferroelectrics

Within the modified four-sublattice model of RbHSO${}_4$ with taking into account the piezoelectric coupling to the strains ${\epsilon }_i$, ${\epsilon }_4$, ${\epsilon }_5$, and ${\epsilon }_6$, the polarization components, static and dynamic dielectric permittivity of clamped and free crystal are calculated in the mean field approximation. At the proper choice of the values of the theory parameters, a satisfactory quantitative description of the available experimental data is obtained.