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Journal of Physical Studies 6(1), 91–108 (2002)
DOI: https://doi.org/10.30970/jps.06.91 THERMODYNAMICS AND DIELECTRIC PROPERTIES OF HYDROGEN BONDED FERROELECTRICS OF KH2PO4 TYPE IN THE CLUSTER APPROXIMATIONR. R. Levitskii, B. M. Lisnii
Institute for Condensed Matter Physics of
the Ukrainian Nat. Acad. Sci. |
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We study thermodynamic and dielectric properties of the KH$_2$PO$_4$ type ferroelectrics within the framework of the proton ordering model with taking into account the tunneling effects. In the four-particle cluster approximation for short-range interaction and mean field approximation for long-range interaction we calculate thermodynamic characteristics and the components of the static dielectric susceptibility tensor, obtain and study the system of equations for the proton ordering parameter, equation for the Curie temperature, as well as Curie-Weiss temperature and constant. We propose an efficient approach to the determination of the optimal values of the model parameters that permit to describe experimental data for thermodynamic and dielectric characteristics of the KDP type crystals properly. Within the frame of the approach we obtain excelent agreement between the theory and experiment for the KH$_2$PO$_4$.
PACS number(s): 77.22.Ch, 77.80.Bh, 77.84.Fa