Journal of Physical Studies 4(2), 190–201 (2000) DOI: https://doi.org/10.30970/jps.04.190 THE INFLUENCE OF SHEAR STRESS σ6 ON PHASE TRANSITION AND PHYSICAL PROPERTIES OF THE KD2PO4 TYPE FERROELECTRICS

I. V. Stasyuk¹, R. R. Levitskii¹, I. R. Zachek², A. P. Moina¹, A. S. Duda¹

¹Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine,
1 Svientsitskii Str., Lviv, UA-79011, Ukraine
²State University "Lvivs'ka Politekhnika",
12 Bandera Str., Lviv, UA-79646, Ukraine

Within the four-particle cluster approximation for the proton ordering model we study the influence of shear stress $σ_6$ on the phase transition, static dielectric, elastic and thermal properties of deuterated KD$_2$PO$_4$ type ferroelectrics. A simplified version of the model of strained KD$_2$PO$_4$ is presented where induced by the strain $ε_6$ splitting of up-down and single-ionized deuteron configurations is neglected. Thermodynamic potentials and physical characteristics of the crystals in the presence of stress $σ_6$ are calculated. The set of the theory parameters providing the best fit to the available experimental data is found. We show that a fair description of the available experimental data for the physical characteristics of the crystal is possible even without taking into account the splitting of up-down deuteron configurations, and that predicted by the theory effects of stress $σ_6$ are similar in both versions of the model.

PACS number(s): 77.80.Bh, 77.84.Fa

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