Distribution Functions and Thermodynamical Properties of KD 2 PO 4 and ND 4 D 2 PO 4 Type Crystals

Within the proton ordering model with taking into account the short-range and long-range interactions as well as tunnelling effects, in the framework of the cluster approximation, we study the thermodynamic and static dielectric properties of the KH 2 PO 4 type ferroelectrics. Theoretical results are compared with the corresponding experimental data and with the results of theoretical calculations of other sources. We show that under the proper choice of the theory parameters, a very good quantitative description of the available experimental data is obtained for the temperature dependence of spontaneous polarization, specific heat, longitudinal and transverse static dielectric permittivities, as well for the Curie-Weiss temperature and constant. Suitability of the model for the description of experimental data for the crystals KH 2 PO 4 , RbH 2 PO 4 , KH 2 AsO 4 , RbH 2 AsO 4 without taking into account striction, fluctuations, and other effects is discussed.

Section: Static Dielectric Permittivitymentioning

confidence: 64%

THERMODYNAMICS AND DIELECTRIC PROPERTIES OF KH_2PO_4, RbH_2PO_4, KH_2AsO_4, RbH_2AsO_4 FERROELECTRICS

Levitskii¹,

Lisnii²,

Baran³

2001

“…As we have already mentioned, the same conclusion was made in [54] within the framework of a simpler model. Later [115,116] the deuteron distribution functions and components of the static dielectric permittivity tensor of the KD 2 PO 4 type ferroelectrics and ND 4 D 2 PO 4 type antiferroelectrics were calculated within the FPCA.…”

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

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.

“…The statistical theory of the phase transitions in ADP type crystals, based on the principles of the proton ordering model proposed in [7][8][9] for the KH 2 PO 4 type crystals, was developed in [4,10]. In [4] the free energy of the proton system was calculated within the four-particle cluster approximation, and possible types of proton ordering were established.…”

Section: Introductionmentioning

confidence: 99%

“…It was noted that a crucial role in the antiferroelectric ordering is played by the long range interactions. In [10] the thermodynamic and dielectric characteristics of deuterated ND 4 D 2 PO 4 type crystals were calculated within the proton ordering model for NH 4 H 2 PO 4 [4] without tunnelling.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Thermodynamics and Dielectric Properties of the Nh_4h_2po_4 Type Antiferroelectrics

Levitskii¹,

Lisnii²,

Baran³

2002

Within the framework of the proton model we study thermodynamic and static dielectric properties of the ADP type antiferroelectrics with taking into account the tunnelling effects of protons on hydrogen bonds. In the fourparticle cluster approximation for the short-range interactions and in the mean field approximation for the long-range interactions we calculate the free energy, entropy, and components of static dielectric susceptibility of the crystals. We also get the system of equations for the sublattice proton order parameter and an equation for the phase transition temperature. We find the values of the theory parameters for the NH 4 H 2 PO 4 and NH 4 H 2 AsO 4 crystals and get a good agreement between the theoretical results and the corresponding experimental data for the temperature dependences of the spontaneous sublattice polarization, proton specific heat, longitudinal and transverse static dielectric permittivities of the crystals.