Journal of Physical Studies 1(4), 577–588 (1997)
DOI: https://doi.org/10.30970/jps.01.577

EXTERNAL PRESSURE INFLUENCE ON PHASE TRANSITION AND PHYSICAL PROPERTIES OF DADP-TYPE ANTIFERROELECTRICS

R. R. Levitskii, I. R. Zachek, A. P. Moina
Institute for Condensed Matter Physics of the Ukrainian Nat. Acad. Sci.
1 Svientsitskii Str., Lviv, UA-290011, Ukraine

Within the antiferroelectric version of the earlier proposed model for a DKDP–type strained crystal we analyze the effects of external pressures on a DADP crystal. In the four–particle cluster approximation we calculate free energy and find the equation for the transition temperature and the explicit expressions for transverse and longitudinal dielectric permittivities and specific heat as functions of pressure. A set of theory parameters providing the best fit to the available experimental data is found. It is predicted that the uniaxial $σ_3$ stress must influence the physical properties of the considered crystal much stronger than the hydrostatic ones. We show that it is possible to describe the pressure effects on the antiferroelectric DADP and ferroelectric DKDP crystals within the same model.