arXiv subjects

A. S. Vdovych

Publications and source records attributed to A. S. Vdovych.

13 recordsLinked to original sources

arXiv2023

Electrocaloric and barocaloric effects in CsH$_2$PO$_4$ ferroelectric

To investigate the caloric effects in the CsH$_2$PO$_4$ ferroelectric, a modified pseudospin model of this crystal is used, which takes into account the dependence of the parameters of interaction between pseudospins on lattice strains. The model also takes into account the dependence of the effective dipole moment of a pseudospin on the order parameter. In the two-particle cluster approximation, the influence of the longitudinal electric field and hydrostatic pressure on the molar entropy of the crystal was studied. The electrocaloric and barocaloric effects were studied. The calculated electrocaloric temperature change is about $1$ K; it can change its sign under the influence of hydrostatic pressure. Barocaloric temperature change is about $-0.5$ K; lattice anharmonicities were not taken into account in its calculations.

cond-mat.mtrl-sci↗

arXiv2022

Effect of hydrostatic pressure on dynamic dielectric characteristics of CsH$_2$PO$_4$ ferroelectric

Based on the pseudospin model of the deformed CsH$_2$PO$_4$ crystal within the Glauber method, the equation for the time-dependent mean value of the pseudospin is obtained, which is solved in the case of small deviations from the equilibrium state. Using the solution of the equation, we find expressions for the longitudinal dynamic dielectric constant and relaxation time. Based on the proposed parameters of the theory, the temperature and frequency dependences of the dynamic dielectric constant and the temperature dependence of the relaxation time are calculated and investigated. A detailed numerical analysis of the obtained results was performed. The influence of hydrostatic pressure on the dynamic characteristics of CsH$_2$PO$_4$ is studied.

cond-mat.mtrl-sci↗

arXiv2020

Effect of hydrostatic pressure and longitudinal electric field on phase transitions and thermodynamic characteristics of quasione-dimensional CsH$_2$PO$_4$ ferroelectric

We propose a two-sublattice proton ordering model for the quasione-dimensional CsH$_2$PO$_4$ ferroelectric with hydrogen bonds, which takes into account linear on lattice strains $u_1$, $u_2$, $u_3$ and $u_5$ contribution to the energy of proton subsystem. The model also takes into account the dependence of effective dipole moments of pseudospins on the order parameters, which enables one to agree the effective dipole moments in paraelectric and ferroelectric phases. Within this model in two-particle cluster approximation on short-range interactions and in the mean field approximation on long-range interactions, there is investigated the behaviour of spontaneous polarization, longitudinal dielectric permittivity and molar heat capacity under the action of hydrostatic pressure and longitudinal electric field. The phase transition into antiferroelectric phase under high pressures is explained. The character of smearing of the paraelectric-ferroelectric phase transition as well as suppression of the antiferroelectric phase at the presence of electric field is studied.

cond-mat.mtrl-sci↗

arXiv2018

Deformation effects in glycinium phosphite ferroelectric

To study the effects appearing under mechanical stresses, we have used the model of glycinium phosphite ferroelectric, modified by taking into account the piezoelectric coupling of ordering structure elements with lattice strains. In the frames of two-particle cluster approximation, the components of polarization vector and static dielectric permittivity tensor of the crystal, as well as its piezoelectric and thermal characteristics are calculated. Influence of shear stresses, hydrostatic and uniaxial pressures on the phase transition and physical characteristics of the crystal is studied.

cond-mat.mtrl-sci↗

arXiv2018

Dynamic properties of NH$_3$CH$_2$COOH$\cdot$H$_2$PO$_3$ ferroelectric

Using a modified pseudospin model of NH$_3$CH$_2$COOH$\cdot$H$_2$PO$_3$ ferroelectric taking into account the piezoelectric coupling with strains $\varepsilon_i$, $\varepsilon_4$, $\varepsilon_5$ and $\varepsilon_6$ within Glauber method in two-particle claster approximation, we have calculated components of dynamic dielectric permittivity tensor and relaxation times of the model. At the proper set of theory parameters, frequency and temperature dependences of the components of permittivity and temperature dependences of the relaxation times are studied. A satisfactory agreement of the theoretical results with experimental data for longitudinal permittivity is obtained.

cond-mat.mtrl-sci↗

arXiv2017

The effect of hydrostatic pressure on thermodynamic characteristics of NH$_3$CH$_2$COOH$\cdot$H$_2$PO$_3$ type ferroelectric materials

The model of NH$_3$CH$_2$COOH$\cdot$H$_2$PO$_3$, modified by taking into account the piezoelectric coupling between the ordering structure elements and the strains $\varepsilon_i$, $\varepsilon_j$, is used for investigation of the effects that appear under external pressures. Within two-particle cluster approximation, the components of polarization vector and static dielectric permittivity tensor of the mechanically clamped and free crystals, their piezoelectric and thermal characteristics are calculated. The effect of hydrostatic pressure on the phase transition and the calculated physical characteristics of the crystal is studied. A good quantitative description of experimental data for these crystals is obtained.

cond-mat.mtrl-sci↗

arXiv2017

Influence of electric fields on dielectric properties of GPI ferroelectric

Using modified microscopic model of GPI by taking into account the piezoelectric coupling with strains $\varepsilon_i$ in the frames of two-particle cluster approximation, the components of polarization vector and static dielectric permittivity tensor of the crystal at applying the external transverse electric fields $E_1$ and $E_3$ are calculated. An analysis of the influence of these fields on thermodynamic characteristics of GPI is carried out. A satisfactory quantitative description of the available experimental data for these characteristics has been obtained at a proper choice of the model parameters.

cond-mat.mtrl-sci↗

arXiv2015

Piezocaloric and multicaloric effect in the KH2PO4 type ferroelectrics

Using the proton ordering model modified by taking into account the dependence of the dipole moments on the order parameter [Vdovych et al, 2014], we explore the piezocaloric and multicaloric effects in the KH$_{2}$PO$_{4}$ type ferroelectrics, caused by the shear stress $σ_6$ and longitudinal electric field $E_3$. The multicaloric effect is shown to be stronger than either electrocaloric or piezocaloric effects, especially at temperatures far from the phase transition.

cond-mat.mtrl-sci↗

arXiv2015

Electrocaloric effect in KH$_2$PO$_4$ family crystals

The proton ordering model for the KH$_{2}$PO$_{4}$ type ferroelectrics is modified by taking into account the dependence of the effective dipole moments on the proton ordering parameter. Within the four-particle cluster approximation we calculate the crystal polarization and explore the electrocaloric effect. Smearing of the ferroelectric phase transition by a longitudinal electric field is described. A good agreement with experiment is obtained.

cond-mat.mtrl-sci↗

arXiv2014

Electrocaloric effect in KH$_2$PO$_4$

The proton ordering model for the KH$_{2}$PO$_{4}$ type ferroelectrics is modified by taking into account non-linear effects, namely, the dependence of the effective dipole moments on the proton ordering parameter. Within the four-particle cluster approximation we calculate the crystal polarization, longitudinal dielectric permittivity, specific heat, and explore the electrocaloric effect. Smearing of the ferroelectric phase transition by the longitudinal electric field is described. A good agreement with experiment is obtained.

cond-mat.mtrl-sci↗

arXiv2013

Transverse Piezoelectric Resonance in KH$_2$PO$_4$ Type Crystals

Within the framework of proton model with taking into account the piezoelectric interaction with the shear strain $\varepsilon_4$, a dynamic dielectric response of KH$_2$PO$_4$ family crystals to the electric field perpendicular to the axis of spontaneous polarizaiton is considered. Piezoelectric resonance frequencies of rectangular thin plates of the crystals cut in the (100) plane (0$^\circ$ X-cut) are calculated.

cond-mat.mtrl-sci↗

arXiv2013

Piezoelectric Resonance in KH2PO4 Type Crystals Revisited

Within the framework of proton ordering model with taking into account the piezoelectric interaction with the shear strain $\varepsilon_6$, a dynamic dielectric response of KD2PO4 type ferroelectrics is considered. An expression for the piezoelectric resonance frequencies of the rectangular thin plate of the crystal cut in the (001) plane is obtained.

cond-mat.mtrl-sci↗

arXiv2012

Longitudinal relaxation of mechanically clamped KH_{2}PO_{4} type crystals

Within the framework of a modified proton ordering model of the KH_{2}PO_{4} family ferroelectric crystals, taking into account a linear over the strain \varepsilon_{6} contribution into the proton system energy, we obtain an expression for longitudinal dynamic dielectric permittivity of a mechanically clamped crystal using the four-particle cluster approximation and the dynamic Glauber approach. At a proper choice of the model parameters, we obtain a good quantitative description of available experimental data for these crystals.

cond-mat.mtrl-sci↗