External pressure influence on ferroelectrics and antiferroelectrics of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">KH</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">PO</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>family: A unified model

Within the framework of the proposed unified proton ordering model for the ferroelectric compounds of the KH 2 PO 4 family, in the four-particle cluster approximation for the short-range interactions and mean field approximation for the long-range interactions, we calculate thermodynamic and longitudinal dynamic characteristics of the KD 2 PO 4 type ferroelectrics and ND 4 D 2 PO 4 type antiferroelectrics. Calculations for partially deuterated K(H 1−x Dx) 2 PO 4 type ferroelectrics and N(H 1−x Dx) 4 (H 1−x Dx) 2 PO 4 type antiferroelectrics are performed within the mean crystal approximation. It is shown that at the proper choice of the theory parameters, a good quantitative description of experimental data for the KH 2 PO 4 family crystals is obtained.

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermodynamics and dynamical properties of the KH_{2}PO_{4} type ferroelectric compounds. A unified model

Levitskii¹,

Zachek²,

Vdovych³

et al. 2009

“…It has been shown in a number of papers [14][15][16][17][18] that an essential improvement of the theoretical description of the wide variety of the experimental data concerning the pressure effect on the physical properties of KDP-type crystals can be achieved with the account of short-range configurational interactions. Therefore, it seems important to perform further theoretical studies of the specific features of the temperature behaviour of longitudinal ε c and transverse ε a dielectric permeability in KDP-type crystals under external pressure, namely to analyze the obtained results in the framework of the proton ordering model with the account of short-range and long-range interactions and proton tunnelling at hydrogenic bonds in the four-particle cluster approximation [19,20]. Such studies could provide information on the physical grounds for the experimentally observed features at the ε c (T ) and ε a (T ) dependences discussed in the present work.…”

Section: Resultsmentioning

confidence: 99%

Temperature and Pressure Effect on the Anisotropy of Dielectric Permeability in KDP and DKDP Crystals

Kedyulich¹,

Slivka²,

Gerzanich³

et al. 2003

Temperature dependences of longitudinal and transverse dielectric permeability of KDP and DKDP crystals are studied at different values of hydrostatic pressure in order to determine the pressure behaviour of the isotropic point for these crystals. The isotropic point temperature in KDP crystals at atmospheric pressure is T i = 186 K at the measuring field frequency 1 kHz and T i = 176 K at the frequency of 1 MHz. In DKDP crystals the isotropic point is achieved at the temperature T i = 300 K ( 1 kHz) and T i = 253 K ( 1 MHz). The hydrostatic pressure increase results in the reduction of the isotropic point temperature with the pressure coefficients ∂T i /∂p = −4.3 K/kbar for KDP and ∂T i /∂p = −2.9 K/kbar for DKDP. The analysis of the experimental results in the framework of the Blinc-Žekš pseudospin formalism has shown a good agreement between the calculated and the experimentally obtained temperature of the isotropic point for KDP crystals.

“…Hydrostatic pressure effects on the system are described within the approach developed in [6]. It is known that the Slater energies ε, w, and w 1 and the components of the long-range interaction matrix J f f (qq ) are proportional to the square of the separation between two possible positions of a deuteron on a bond -D-site distance δ.…”

Section: Model Of Strained Kd 2 Po 4 Type Crystalmentioning

confidence: 99%

“…The pressure derivatives of these characteristics for KH 2 PO 4 and KD 2 PO 4 were already successfully described within the proton ordering model by Blinc [2] and Tortsveit [3]. In our recent papers [4][5][6], we developed a unified approach allowing one to consistently describe pressure effects on transition temperature and on static dielectric properties of several ferroelectrics and antiferroelectrics with general formula MeD 2 XO 4 , where Me = K, Rb, ND 4 , X = P, As.…”

Section: Introductionmentioning

confidence: 99%

Longitudinal Dielectric Relaxation in Kd_2po_4 Under Hydrostatic Pressure

Levitskii¹,

Zachek²,

Moina³

et al. 2002

Within the model proposed earlier, we study the effect of hydrostatic pressure on relaxational dynamics of deuterated KD 2 PO 4 type ferroelectrics. Within the four particle approximation for deuteron ordering model and using the Glauber approach, we calculate the longitudinal dynamic dielectric permittivity of the strained crystal. Possible pressure dependences of the permittivity and relaxation times are discussed.