Nonlinear Dielectric Response Research Articles

Linear and Nonlinear Dielectric Response of Intrinsically Disordered Proteins.

Linear and nonlinear dielectric responses of solutions of intrinsically disordered proteins (IDPs) were analyzed by combining molecular dynamics simulations with formal theories. A large increment of the linear dielectric function over that of the solvent is found and related to large dipole moments of IDPs. The nonlinear dielectric effect (NDE) of the IDP far exceeds that of the bulk electrolyte, offering a route to interrogate protein conformational and rotational statistics and dynamics. Conformational flexibility of the IDP makes the dipole moment statistics consistent with the gamma/log-normal distributions and contributes to the NDE through the dipole moment's non-Gaussian parameter. The intrinsic non-Gaussian parameter of the dipole moment combines with the protein osmotic compressibility in the nonlinear dielectric susceptibility when dipolar correlations are screened by the electrolyte. The NDE is dominated by dipolar correlations when electrolyte screening is reduced.

Effect of oxygen defects on ferroelectric oxides: Correlation between linear and nonlinear dielectric responses

Oxygen defects are introduced into PbZr0.5Ti0.5O3 films and their impact on ferroelectric behavior, linear dielectric response (LDR), and nonlinear dielectric response (NDR) is studied. Apart from a notable decrease in both polarization and LDR permittivity, the frequency spectra of LDR exhibit a distinctive loss peak. The peak position varies with temperature and oxygen defect concentration. NDR parameters, including the Rayleigh coefficient (α1), the slope (α2) correlating the imaginary part of permittivity with the ac electric field, and the slope (k) between the real and the imaginary parts of permittivity, demonstrate diverse behaviors in response to temperature and oxygen defect concentration. The similarity in the frequency spectra of tanδ and 1/k reveals the correlation between LDR and NDR induced by the presence of oxygen defects. These observations are attributed to the behavior of the single and composite defects associated with oxygen vacancies.

An implicit electrolyte model for plane wave density functional theory exhibiting nonlinear response and a nonlocal cavity definition.

We have developed and implemented an implicit electrolyte model in the Vienna Ab initio Simulation Package (VASP) that includes nonlinear dielectric and ionic responses as well as a nonlocal definition of the cavities defining the spatial regions where these responses can occur. The implementation into the existing VASPsol code is numerically efficient and exhibits robust convergence, requiring computational effort only slightly higher than the original linear polarizable continuum model. The nonlinear + nonlocal model is able to reproduce the characteristic "double hump" shape observed experimentally for the differential capacitance of an electrified metal interface while preventing "leakage" of the electrolyte into regions of space too small to contain a single water molecule or solvated ion. The model also gives a reasonable prediction of molecular solvation free energies as well as the self-ionization free energy of water and the absolute electron chemical potential of the standard hydrogen electrode. All of this, combined with the additional ability to run constant potential density functional theory calculations, should enable the routine computation of activation barriers for electrocatalytic processes.

Studies on the nonlinear dielectric response in ferroelectric–dielectric composite system

The nonlinear dielectric response (NDR) of Bi3.25La0.75Ti3O12–Al2O3 systems has been studied. To reveal the effects of the dielectric layer (DL) systematically, a method based on the equivalent circuit analysis and parametric study is proposed. The consistency between the calculated results and the experimental results manifests the validity of the method. In addition to the Rayleigh coefficients varying monotonically with the capacitance of DL, it is revealed that the slope between the real and the imaginary parts of the complex capacitance under different ac voltages is related to the relative loss values of DL and the ferroelectric layer. The frequency dependence of the NDR parameters is also discussed. The method established in this work is useful for research on the devices based on the ferroelectric–dielectric system and the ultra-thin ferroelectric films.

Structural Changes and Very-Low-Frequency Nonlinear Dielectric Response of XLPE Cable Insulation under Thermal Aging.

The structural changes and very-low-frequency (VLF) nonlinear dielectric responses are measured to evaluate the aging state of cross-linked polyethylene (XLPE) in power cables under various thermal aging conditions. For this purpose, the accelerated thermal aging experiments were performed on XLPE insulation materials at 90 °C, 120 °C and 150 °C with different durations of 240 h, 480 h and 720 h, respectively. The Fourier transform infrared spectrum (FTIR) characterization and differential scanning calorimeter (DSC) were tested to analyze the influence of different aging on physicochemical properties of XLPE insulation. Besides, the VLF dielectric spectra show that the permittivity and dielectric loss change significantly in the VLF range from 1 mHz to 0.2 Hz. A voltage-current (U-I) hysteresis curve referring to a standard sinusoidal voltage and the response current were introduced to characterize the nonlinear dielectric properties of XLPE insulation caused by thermal aging.

Polarity-dependence of the nonlinear dielectric response in interfacial water.

Molecular dynamics simulations are used to study the nonlinear dielectric responses of a confined aqueous film in a planar nanopore under perpendicular electric fields at varied voltages between confining graphene sheets. Dielectric saturation reminiscent of the bulk phase behavior is prevalent at very strong fields, whereas we observe a nonmonotonic permittivity dependence on the electric field at intermediate strengths where field-alignment and spontaneous polarization of interfacial water are of comparable magnitude. The coupling between the two effects results in distinct dielectric responses at opposite confinement walls. The normal component of both the differential dielectric constant and dielectric difference constant tensors averaged over the region closer to the wall under an incoming electric field (field pointing from the liquid to the solid phase) initially increases with the strength of the imposed field. The differential permittivity peaks at a field strength previously shown to offset the surface-induced orientation bias of hydration molecules at this wall. Further strengthening of the field results in a conventional saturation behavior. At the opposite wall (subject to outgoing field) and in the central region of the water slab, the nonlinear dielectric response resembles bulklike saturation. The conditions at the permittivity extremum coincide with the window of accelerated reorientation rates of interfacial water molecules under an incoming field we uncovered in earlier molecular dynamics analyses.

Simulating dielectric spectra: A demonstration of the direct electric field method and a new model for the nonlinear dielectric response.

We demonstrate a method to compute the dielectric spectra of fluids in molecular dynamics (MD) by directly applying electric fields to the simulation. We obtain spectra from MD simulations with low magnitude electric fields (≈0.01 V/Å) in agreement with spectra from the fluctuation-dissipation method for water and acetonitrile. We examine this method's trade-off between noise at low field magnitudes and the nonlinearity of the response at higher field magnitudes. We then apply the Booth equation to describe the nonlinear response of both fluids at low frequency (0.1GHz) and high field magnitude (up to 0.5 V/Å). We develop a model of the frequency-dependent nonlinear response by combining the Booth description of the static nonlinear dielectric response of fluids with the frequency-dependent linear dielectric response of the Debye model. We find good agreement between our model and the MD simulations of the nonlinear dielectric response for both acetonitrile and water.

Nonlinear characteristics of the oil-paper insulation system during the polarization and depolarization process

The oil-immersed transformer plays a pivotal role in the power network. Its insulation stability is essential. At present, the application of time-domain dielectric response technology in insulation detection of oil-immersed equipment is relatively mature. However, there is a contradiction between increasing the test excitation amplitude to improve the test accuracy and the nonlinear response characteristics of the test dielectric at high-voltage excitation. The assessment theories all depend on the laboratory test results, and inaccurate test results will affect the assessment results. Therefore, this paper prepared several groups of insulation-scaled aging models in the laboratory and studied the effects of temperature and test excitation amplitude on the polarization and depolarization characteristics of the models. During the polarization process, the electric intensity variation was calculated. Meanwhile, at the time-varying electric field, the influence mechanism of electric intensity on the response current caused by the charge escaping from the trap during the polarization process was obtained. This paper quantified the relationship between the aging state and the height of the interfacial polarization barrier. The study of nonlinear dielectric response in the time domain will help to improve the accuracy of test results when diagnosing the insulation performance of oil-immersed transformers.

Dynamic of polar nanoregions and its impact on the pyroelectric and dielectric properties in paraelectric KTN materials

AbstractThe origin of the excellent properties of KTN‐based materials around Curie temperature (TC), which should be originated form the motion of polar nanoregions (PNRs), has attracted considerable research interest. In this paper, the relaxation of a KTa0.63Nb0.37O3 single crystal is discussed with the temperature dependence of permittivity. Moreover, its pyroelectric effect above TC is investigated. In detail, the pyroelectric coefficient decreases from ∼110.0 to ∼13.0 μC/(m2 K), with the temperature increasing from 22 to 33°C, and finally reduces to 0 at 100°C with PNRs disappear. Moreover, the dynamic dielectric nonlinearity for the KTN single crystal is studied in the paraelectric phase. To investigate these mechanisms, the amplitude and phase angle of the first and third harmonics under various electric fields, frequencies, and temperatures are analyzed. As a result, the motions of PNRs induced by electric field, which is pinned and depinned by the defect, are presented to explain the nonlinear dielectric response observed in the paraelectric KTN single crystal.

To age or not to age: Anatomy of a supercooled liquid's response to a high alternating electric field.

Physical aging and structural recovery are the processes with which the structure of a system approaches equilibrium after some perturbation. Various methods exist, that initiate structural recovery, such as changing the temperature or applying a strong, external static field. This work is concerned with high alternating electric fields and their suitability to study structural recovery and aging. The present work demonstrates that rationalizing the nonlinear dielectric response of a supercooled liquid to high-amplitude ac-fields requires multiple fictive temperatures. This feature is in stark contrast to structural recovery after a temperature down-jump or a considerable increase in the static electric field, for which a single parameter, the fictive temperature or material time, describes the structural change. In other words, the structural recovery from a high ac-field does not adhere to time aging-time superposition, which is so characteristic of genuine aging processes.

Nonlinear dielectric response of dilute protein solutions.

A theory for the nonlinear dielectric response of dilute protein solutions is presented. The field-dependent dielectric function of the protein solution changes linearly with the electric field squared in the lowest order. The slope of this dependence is expressed in terms of the protein dipole moment M0, its volume fraction in solution η0, and the second osmotic virial coefficient. For practical conditions, the nonlinear dielectric response scales as η03M08. This strong dependence on the protein dipole moment and concentration establishes a sharp contrast between the nonlinear response of solvated proteins relative to the surrounding polar solvent. Nonlinear dielectric response can serve as a sensitive tool for monitoring protein conformations and physiological activity.

Strong-Field Control of Plasmonic Properties in Core–Shell Nanoparticles

The strong-field control of plasmonic nanosystems opens up new perspectives for nonlinear plasmonic spectroscopy and petahertz electronics. Questions, however, remain regarding the nature of nonlinear light-matter interactions at sub-wavelength spatial and ultrafast temporal scales. Addressing this challenge, we investigated the strong-field control of the plasmonic response of Au nanoshells with a SiO$_2$ core to an intense laser pulse. We show that the photoelectron energy spectrum from these core-shell nanoparticles displays a striking transition between the weak and strong-field regime. This observed transition agrees with the prediction of our modified Mie-theory simulation that incorporates the nonlinear dielectric nanoshell response. The demonstrated intensity-dependent optical control of the plasmonic response in prototypical core-shell nanoparticles paves the way towards ultrafast switching and opto-electronic signal modulation with more complex nanostructures.

Complex Oxides under Simulated Electric Field: Determinants of Defect Polarization in ABO3 Perovskites.

Polarization of ionic and electronic defects in response to high electric fields plays an essential role in determining properties of materials in applications such as memristive devices. However, isolating the polarization response of individual defects has been challenging for both models and measurements. Here the authors quantify the nonlinear dielectric response of neutral oxygen vacancies, comprised of strongly localized electrons at an oxygen vacancy site, in perovskite oxides of the form ABO3. Their approach implements a computationally efficient local Hubbard U correction in density functional theory simulations. These calculations indicate that the electric dipole moment of this defect is correlated positively with the lattice volume, which they varied by elastic strain and by A‐site cation species. In addition, the dipole of the neutral oxygen vacancy under electric field increases with increasing reducibility of the B‐site cation. The predicted relationship among point defect polarization, mechanical strain, and transition metal chemistry provides insights for the properties of memristive materials and devices under high electric fields.

Intrinsic and Extrinsic Contributions in Nonlinear Dielectric Response of (Bi0.5Na0.3K0.2)TiO3-(Ba0.8Ca0.2)TiO3 -Based SrTiO3 Ceramics Driven by the Rayleigh Model

Intrinsic and Extrinsic Contributions in Nonlinear Dielectric Response of (Bi0.5Na0.3K0.2)TiO3-(Ba0.8Ca0.2)TiO3 -Based SrTiO3 Ceramics Driven by the Rayleigh Model

Interfacial magneto-plasticity in partially oxidized magnetite inferred from linear and nonlinear dielectric response

In partially oxidized polycrystalline magnetite, defects/dislocations are formed at the grain/interphase boundaries among the remaining magnetite and oxidized phases. Here, the studied sample is a pellet with the composition of Fe3O4 and α-Fe2O3(3:7), which is obtained by annealing partially air-oxidized polycrystalline Fe3O4. To probe the dislocation behavior in it under the magnetic field, linear and nonlinear dielectric spectroscopy has been utilized under three conditions: before applying the magnetic field, under a magnetic field after cooling at the same field, and after removing the magnetic field. An excessive qualitative and quantitative difference between the dielectric data—both linear and nonlinear harmonic components—taken in the first two protocols has been observed. The dielectric data feature remains like the field-cooled measurement after magnetic field withdrawal. In the field-cooled dielectric frequency spectrum, grain boundary relaxation shows a glass transition above 110 K. This phenomenon occurs mainly due to the plastic deformation through the dislocation movements at the boundaries by the magnetostrictive strain produced in the magnetite grains below the Verwey transition (TV). The dislocations freeze into a glassy phase below the TV of magnetite. The interaction among the dislocations and the boundaries are responsible for showing the nonlinear features.

Nonlinear dielectric response and positive dielectric tunability in antipolar CaTiSiO5

AbstractDielectric tunability has been extensively investigated in ferroelectric materials, which exhibit a negative tunability of dielectric permittivity in an external electric field. In contrast, positive tunability is rare and has been reported only in a few antiferroelectric materials. We present positive (and negative) tunability in the titanite, CaTiSiO5. The dielectric property of CaTiSiO5 was measured up to an extraordinarily high electric field of 40 MV/m. A nonlinear polarization field loop with no hysteresis was obtained. The dielectric permittivity of εr ~ 25 increases up to εr ~ 40 at 20 MV/m and room temperature. Although titanite has an antipolar structure and is expected to be “antiferroelectric,” its dielectric response in high electric fields up to ~40 MV/m differs from that of conventional antiferroelectrics. We demonstrate that the phase‐transition temperature and dielectric tunability could be modulated through the chemical substitution of Ca1−xLaxTiSi1−xAlxO5, in which the destabilization of the long‐range antipolar order is revealed by transmission electron microscopy analysis. These results indicate that the observed dielectric response to an electric field may originate from the unique features of the antipolar and domain structures in CaTiSiO5.

Material Design Strategy for Enhancement of Readback Signal Intensity in Ferroelectric Probe Data Storage.

Ferroelectric probe data storage (FPDS) based on scanning nonlinear dielectric microscopy is expected as a next-generation data storage method with its large potential for improvement of the recording density. However, this novel method has a problem of low reading speed. To overcome this problem, a novel ferroelectric recording medium with large nonlinear permittivity is required because this data storage method uses the nonlinear dielectric response induced by small-amplitude ac bias to detect the bit data recorded in the form of polarization direction. Therefore, this article discusses nonlinear permittivity enhancement from the viewpoint of data storage application in the framework of the phenomenological theory. We reveal that the Curie-point control is one of the key techniques in material design for FPDS because nonlinear permittivity increases precipitously as the Curie temperature is approached, as with the linear permittivity and piezoelectric constants. A similar conclusion is also obtained through actual measurements of nonlinear permittivity in LiTaO3 single crystals. On the other hand, we also reveal that there is a tradeoff relationship between nonlinear permittivity and polarization stability. To avoid this undesirable situation in data storage applications, pinning-site control will also be important. We also propose to employ a double-layer structure in the ferroelectric recording media for further improvement.

Pretransitional Effects of the Isotropic Liquid-Plastic Crystal Transition.

We report on strong pretransitional effects across the isotropic liquid–plastic crystal melting temperature in linear and nonlinear dielectric response. Studies were carried out for cyclooctanol (C8H16O) in the unprecedented range of temperatures 120 K < T < 345 K. Such pretransitional effects have not yet been reported in any plastic crystals. Results include the discovery of the experimental manifestation of the Mossotti Catastrophe behavior, so far considered only as a hypothetical paradox. The model interpretations of experimental findings are proposed. We compare the observed pretransitional behavior with the one observed in octyloxycyanobiphenyl (8OCB), typical liquid crystal (LC), displaying a reversed sequence of phase transitions in orientational and translational degrees of order on varying temperature. Furthermore, in its nematic phase, we demonstrate first-ever observed temperature-driven crossover between regions dominated by isotropic liquid and smectic A pretransitional fluctuations. We propose a pioneering minimal model describing plastic crystal phase behavior where we mimic derivation of classical Landau-de Gennes-Ginzburg modeling of Isotropic-Nematic-Smectic A LC phase behavior.

Modeling ferroelectric domain walls motion and nonlinear dielectric response

The dynamics of ferroelectrics domain walls is modeled by the equation of a particle in a force field. It is considered that over the domain walls act the forces due to the interaction with an external electric field the internal mechanical and electric interactions represented by the effective potential and the friction force produced by the interaction of domain walls with phonons and point defects. The effective potential is determined assuming that the dielectric permittivity dependence on the electric field is given by the relation Simulations reproduce several important features of nonlinear dielectric behavior of ferroelectrics in good agreement with experimental data. Defects are included in the model introducing a generalized damping force with which it is possible to explain the high losses observed for subswitching electric fields. This theoretical approach can be useful in domain wall engineering and to develop new applications of ferroelectrics.

Non-linear dielectric response of layered CuInP2S6 and Cu0.9Ag0.1InP2S6 crystals

In this work, we report on the results of the examination of the nonlinear dielectric response of layered ferrielectic CuInP2S6 and Cu0.9Ag0.1InP2S6 crystals. The temperature behaviour of the nonlinear dielectric properties of ferrielectic CuInP2S6 and Cu0.9Ag0.1InP2S6 is found to be consistent with Landau theory. The additional peak of the third-order nonlinear susceptibility in these crystals, below the phase transition temperature, is strongly influenced by the electric field amplitude, and it is caused by the ferroelectric domain dynamics. The nonzero value of the second-order susceptibility and the mismatch between the temperatures of linear and third-order susceptibilities indicate that some polarisation exists above the phase transition temperature.