Showing papers on "Debye published in 2017"
TL;DR: An extremely large-scale vibrational mode analysis of a model amorphous solid finds that the scaling law predicted by the mean-field theory is violated at low frequency, and in the continuum limit, the vibrational modes converge to a mixture of phonon modes that follow the Debye law and soft localized modes that following another universal non-Debye scaling law.
Abstract: The low-frequency vibrational and low-temperature thermal properties of amorphous solids are markedly different from those of crystalline solids. This situation is counterintuitive because all solid materials are expected to behave as a homogeneous elastic body in the continuum limit, in which vibrational modes are phonons that follow the Debye law. A number of phenomenological explanations for this situation have been proposed, which assume elastic heterogeneities, soft localized vibrations, and so on. Microscopic mean-field theories have recently been developed to predict the universal non-Debye scaling law. Considering these theoretical arguments, it is absolutely necessary to directly observe the nature of the low-frequency vibrations of amorphous solids and determine the laws that such vibrations obey. Herein, we perform an extremely large-scale vibrational mode analysis of a model amorphous solid. We find that the scaling law predicted by the mean-field theory is violated at low frequency, and in the continuum limit, the vibrational modes converge to a mixture of phonon modes that follow the Debye law and soft localized modes that follow another universal non-Debye scaling law.
224 citations
TL;DR: Attempts at fitting the experimental spectrum using the gLST relation as a constraint indicate that the traditional way of fitting the excess response with secondary and tertiary Debye relaxations is problematic.
Abstract: We critically review the literature on the Debye absorption peak of liquid water and the excess response found on the high frequency side of the Debye peak. We find a lack of agreement on the microscopic phenomena underlying both of these features. To better understand the molecular origin of Debye peak we ran large scale molecular dynamics simulations and performed several different distance-dependent decompositions of the low frequency dielectric spectra, finding that it involves processes that take place on scales of 1.5-2.0 nm. We also calculated the k-dependence of the Debye relaxation, finding it to be highly dispersive. These findings are inconsistent with models that relate Debye relaxation to local processes such as the rotation/translation of molecules after H-bond breaking. We introduce the spectrumfitter Python package for fitting dielectric spectra and analyze different ways of fitting the high frequency excess, such as including one or two additional Debye peaks. We propose using the generalized Lydanne-Sachs-Teller (gLST) equation as a way of testing the physicality of model dielectric functions. Our attempts at fitting the experimental spectrum using the gLST relation as a constraint indicate that the traditional way of fitting the excess response with secondary and tertiary Debye relaxations is problematic. All of our work is consistent with the recent theory of Popov et al. (2016) that Debye relaxation is due to the migration of Bjerrum-like defects in the hydrogen bond network. Under this theory, the mechanism of Debye relaxation in liquid water is similar to the mechanism in ice, but the heterogeneity and power-law dynamics of the H-bond network in water results in excess response on the high frequency side of the peak.
60 citations
TL;DR: What insight can be gained from the nonlinear responses that are not available from dielectric relaxation results obtained in the linear regime are emphasized.
Abstract: Dielectric relaxation measurements probe how the polarization of a material responds to the application of an external electric field, providing information on structure and dynamics of the sample. In the limit of small fields and thus linear response, such experiments reveal the properties of the material in the same thermodynamic state it would have in the absence of the external field. At sufficiently high fields, reversible changes in enthalpy and entropy of the system occur even at constant temperature, and these will in turn alter the polarization responses. The resulting nonlinear dielectric effects feature field induced suppressions (saturation) and enhancements (chemical effect) of the amplitudes, as well as time constant shifts towards faster (energy absorption) and slower (entropy reduction) dynamics. This review focuses on the effects of high electric fields that are reversible and observed at constant temperature for single component glass-forming liquids. The experimental challenges involved in nonlinear dielectric experiments, the approaches to separating and identifying the different sources of nonlinear behavior, and the current understanding of how high electric fields affect dielectric materials will be discussed. Covering studies from Debye's initial approach to the present state-of-the-art, it will be emphasized what insight can be gained from the nonlinear responses that are not available from dielectric relaxation results obtained in the linear regime.
48 citations
TL;DR: It turns out that the improved setup allows to unambiguously identify the JG β-process, which shows almost identical properties in DDLS as in the dielectric spectra, but a Debye relaxation is not present in the DDLS data and can be excluded down to a level of 2.5% of the α-process amplitude.
Abstract: We revisit the reorientational dynamics of 1-propanol as a prototype of a monohydroxy alcohol and H-bonding system by dielectric spectroscopy (DS) and depolarized dynamic light scattering (DDLS). In particular, we address the question of whether the Debye relaxation, which is seen as a dominant process in DS, is visible in light scattering and discuss how the Johari–Goldstein (JG) β-process, which is also a prominent feature of the dielectric spectrum, appears in photon correlation spectroscopy. For that purpose we performed depolarized photon correlation experiments with an improved setup and performed additional time domain dielectric experiments which gives us the possibility to compare dielectric and light scattering data in a broad temperature range. It turns out that the improved setup allows to unambiguously identify the JG β-process, which shows almost identical properties in DDLS as in the dielectric spectra, but a Debye relaxation is not present in the DDLS data and can be excluded down to a lev...
42 citations
TL;DR: In this paper, a dielectric sample can be described by Debye's model at each frequency, and a method based on Cole's treatment is proposed for the direct estimation at experimental frequencies of relaxation times and the corresponding static and infinite-frequency permittivities.
Abstract: Assuming that a dielectric sample can be described by Debye's model at each frequency, a method based on Cole's treatment is proposed for the direct estimation at experimental frequencies of relaxation times and the corresponding static and infinite-frequency permittivities. These quantities and the link between dielectric strength and mean molecular dipole moment at each frequency could be useful to analyze dielectric relaxation processes. The method is applied to samples that follow a Cole–Cole or a Cole–Davidson dielectric function. A physical interpretation of these dielectric functions is proposed. The behavior of relaxation time with frequency can be distinguished between the two dielectric functions. The proposed method can also be applied to samples following a Navriliak–Negami or any other dielectric function. The dielectric relaxation of a nanofluid consisting of graphene nanoparticles dispersed in the oil squalane is reported and discussed within the novel framework.
30 citations
TL;DR: The Debye ring method was used to investigate the 2D PC particle spacing, and ordering at the air-solution interface of NaCl solutions, and for 2DPC arrays attached to glass slides, and Surprisingly, the2DPC ordering does not monotonically decrease as the salt concentration increases.
Abstract: We fabricate 2D photonic crystals (2DPC) by spreading a dispersion of charged colloidal particles (diameters = 409, 570, and 915 nm) onto the surface of electrolyte solutions using a needle tip flow method. When the interparticle electrostatic interaction potential is large, particles self-assemble into highly ordered hexagonal close packed (hcp) monolayers. Ordered 2DPC efficiently forward diffract monochromatic light to produce a Debye ring on a screen parallel to the 2DPC. The diameter of the Debye ring is inversely proportional to the 2DPC particle spacing, while the Debye ring brightness and thickness depends on the 2DPC ordering. The Debye ring thickness increases as the 2DPC order decreases. The Debye ring ordering measurements of 2DPC attached to glass slides track measurements of the 2D pair correlation function order parameter calculated from SEM micrographs. The Debye ring method was used to investigate the 2DPC particle spacing, and ordering at the air–solution interface of NaCl solutions, and for 2DPC arrays attached to glass slides. Surprisingly, the 2DPC ordering does not monotonically decrease as the salt concentration increases. This is because of chloride ion adsorption onto the anionic particle surfaces. This adsorption increases the particle surface charge and compensates for the decreased Debye length of the electric double layer when the NaCl concentration is below a critical value.
29 citations
TL;DR: In this paper, structural and physical properties of the Co2VZ (Z = Al, Ga) Heusler alloys, with L21 structure, through first-principles calculations involving the full potential linearized augmented plane-wave method within density functional theory.
Abstract: We report on the investigation of the structural and physical properties of the Co2VZ (Z = Al, Ga) Heusler alloys, with L21 structure, through first-principles calculations involving the full potential linearized augmented plane-wave method within density functional theory. These physical properties mainly revolve around the electronic, magnetic and thermodynamic properties. By using the Perdew–Burke–Ernzerhof generalized gradient approximation, the calculated lattice constants and spin magnetic moments were found to be in good agreement with the experimental data. Furthermore, the thermal effects using the quasi-harmonic Debye model have been investigated in depth while taking into account the lattice vibrations, the temperature and the pressure effects on the structural parameters. The heat capacities, the thermal expansion coefficient and the Debye temperatures have also been determined from the non-equilibrium Gibbs functions. An application of the atom in molecule theory is presented and discussed in order to analyze the bonding nature of the Heusler alloys. The focus is on the mixing of the metallic and covalent behavior of Co2VZ (Z = Al, Ga) Heusler alloys.
29 citations
TL;DR: In this paper, the trajectories of fast atoms at crystal surfaces are described in terms of individual inelastic collisions with surface atoms taking place along the projectile trajectory and leading to vibrational excitation of the local Debye oscillator.
Abstract: The diffraction of fast atoms at crystal surfaces is ideal for a detailed investigation of the surface electronic density. However, instead of sharp diffraction spots, most experiments show elongated streaks characteristic of inelastic diffraction. This paper describes these inelastic profiles in terms of individual inelastic collisions with surface atoms taking place along the projectile trajectory and leading to vibrational excitation of the local Debye oscillator. A quasielastic regime where only one inelastic event contributes is identified as well as a mixed quantum-classical regime where several inelastic collisions are involved. These regimes describe a smooth evolution of the scattering profiles from sharp spots to elongated streaks merging progressively into the classical diffusion regime.
27 citations
TL;DR: In this paper, the information-theoretic measures for hydrogen-like ions immersed in weakly coupled plasmas modeled by Debye-Huckel potential are quantified in both position and momentum spaces.
Abstract: Recent development of information theory provides researchers an alternative and useful tool to quantitatively investigate the variation of the electronic structure when atoms interact with the external environment. In this work, we make systematic studies on the information-theoretic measures for hydrogen-like ions immersed in weakly coupled plasmas modeled by Debye-Huckel potential. Shannon entropy, Fisher information, and Fisher-Shannon complexity in both position and momentum spaces are quantified in high accuracy for the hydrogen atom in a large number of stationary states. The plasma screening effect on embedded atoms can significantly affect the electronic density distributions, in both conjugate spaces, and it is quantified by the variation of information quantities. It is shown that the composite quantities (the Shannon entropy sum and the Fisher information product in combined spaces and Fisher-Shannon complexity in individual space) give a more comprehensive description of the atomic structure ...
25 citations
23 Aug 2017
TL;DR: In this article, the structural, elasto-mechanical thermo-electronic and thermodynamic properties of XMoO3 (X = Sr, Ba) have been evaluated within different exchange correlation potentials.
Abstract: Highly precise and accurate density functional theory has been used to check the structural, elasto-mechanical thermo-electronic and thermodynamic properties of XMoO3 (X = Sr, Ba). The study was accomplished within different exchange correlation potentials like (GGA, GGA + U, mBJ, and GGA + U + SOC). The optimization for both the compounds was achieved for paramagnetic, ferromagnetic and anti-ferromagnetic phases and the compounds were found to have paramagnetic stable phase. The spin polarized band structure and density of states present metallic nature for both the compounds. The symmetric spin polarized band for both (up, down) states and negligible spin magnetic moment also confirm the paramagnetic nature of these compounds. The post DFT treatment through Boltztrap code was used to check the temperature dependence of electrical conductivity. The elastic constants and mechanical properties like Young modulus, shear modulus, Poisson ratio and anisotropic factor have also been calculated. The calculated value of B/G ratio and Cauchy pressure show that both compounds establish ductile nature. Debye temperature along with melting temperature for both the compounds was predicted. Further the nature of thermodynamic parameters like heat capacity and Debye temperature were also checked under pressure and temperature variation using quasi-harmonic Debye approximation.
24 citations
TL;DR: The time scale on which the thermovoltage develops is the Debye time, 1/Dκ^{2}, where D is the Brownian diffusion coefficient of both ion species, and κ^{-1} is theDebye length, and the concentration gradient due to the Soret effect develops on the bulk diffusion time, L^{2}/D, where L is the distance between the electrodes.
Abstract: Thermoelectrics are increasingly being studied as promising electrical generators in the ongoing search for alternative energy sources. In particular, recent experimental work has examined thermoelectric materials containing ionic charge carriers; however, the majority of mathematical modeling has been focused on their steady-state behavior. Here, we determine the time scales over which the diffuse charge dynamics in ionic thermoelectrochemical systems occur by analyzing the simplest model thermoelectric cell: a binary electrolyte between two parallel, blocking electrodes. We consider the application of a temperature gradient across the device while the electrodes remain electrically isolated from each other. This results in a net voltage, called the thermovoltage, via the Seebeck effect. At the same time, the Soret effect results in migration of the ions toward the cold electrode. The charge dynamics are described mathematically by the Poisson-Nernst-Planck equations for dilute solutions, in which the ion flux is driven by electromigration, Brownian diffusion, and thermal diffusion under a temperature gradient. The temperature evolves according to the heat equation. This nonlinear set of equations is linearized in the (experimentally relevant) limit of a "weak" temperature gradient. From this, we show that the time scale on which the thermovoltage develops is the Debye time, 1/Dκ^{2}, where D is the Brownian diffusion coefficient of both ion species, and κ^{-1} is the Debye length. However, the concentration gradient due to the Soret effect develops on the bulk diffusion time, L^{2}/D, where L is the distance between the electrodes. For thin diffuse layers, which is the condition under which most real devices operate, the Debye time is orders of magnitude less than the diffusion time. Therefore, rather surprisingly, the majority of ion motion occurs after the steady thermovoltage has developed. Moreover, the dynamics are independent of the thermal diffusion coefficients, which simply set the magnitude of the steady-state thermovoltage.
TL;DR: The combined results from dielectric spectroscopy and AC nanocalorimetry on the plastic crystal of ethanol suggest the occurrence of a Debye process also in the plastic Crystal phase.
Abstract: Physical vapor deposition has been used to prepare glasses of ethanol. Upon heating, the glasses transformed into the supercooled liquid phase and then crystallized into the plastic crystal phase. The dynamic glass transition of the supercooled liquid is successfully measured by AC nanocalorimetry, and preliminary results for the plastic crystal are obtained. The frequency dependences of these dynamic glass transitions observed by AC nanocalorimetry are in disagreement with conclusions from previously published dielectric spectra of ethanol. Existing dielectric loss spectra have been carefully re-evaluated considering a Debye peak, which is a typical feature in the dielectric loss spectra of monohydroxy alcohols. The re-evaluated dielectric fits reveal a prominent dielectric Debye peak, a smaller and asymmetrically broadened peak, which is identified as the signature of the structural α-relaxation and a Johari-Goldstein secondary relaxation process. This new assignment of the dielectric processes is supported by the observation that the AC nanocalorimetry dynamic glass transition temperature, Tα, coincides with the dielectric structural α-relaxation process rather than the Debye process. The combined results from dielectric spectroscopy and AC nanocalorimetry on the plastic crystal of ethanol suggest the occurrence of a Debye process also in the plastic crystal phase.
TL;DR: Commer et al. as discussed by the authors proposed a finite-difference time-domain scheme for modeling transient electromagnetic signals containing induced polarization effects from 3-D distributions of polarizable media, which can be used to solve the non-dispersive problem of discrete dispersive Maxwell system.
Abstract: Author(s): Commer, M; Petrov, PV; Newman, GA | Abstract: The finite-difference time-domain scheme is augmented in order to treat the modelling of transient electromagnetic signals containing induced polarization effects from 3-D distributions of polarizable media. Compared to the non-dispersive problem, the discrete dispersive Maxwell system contains costly convolution operators. Key components to our solution for highly digitized model meshes are Debye decomposition and composite memory variables. We revert to the popular Cole-Cole model of dispersion to describe the frequency-dependent behaviour of electrical conductivity. Its inversely Laplace-transformed Debye decomposition results in a series of time convolutions between electric field and exponential decay functions, with the latter reflecting each Debye constituents' individual relaxation time. These function types in the discrete-time convolution allow for their substitution by memory variables, annihilating the otherwise prohibitive computing demands. Numerical examples demonstrate the efficiency and practicality of our algorithm.
TL;DR: In this paper, the effect of Debye and quantum plasma environment on the structural properties such as spin orbit splitting, relativistic mass correction and Darwin term for a few iso-electronic members of hydrogen viz. C5 +, O7 +, Ne9 +, Mg11 +, Si13 +, S15 +, Ar17 +, Ca19 + and Ti21 + has been analyzed systematically for the first time for a range of coupling strengths of the plasma.
Abstract: The effect of Debye and quantum plasma environment on the structural properties such as spin orbit splitting, relativistic mass correction and Darwin term for a few iso-electronic members of hydrogen viz. C5 +, O7 +, Ne9 +, Mg11 +, Si13 +, S15 +, Ar17 +, Ca19 + and Ti21 + has been analysed systematically for the first time for a range of coupling strengths of the plasma. The Debye plasma environment has been treated under a standard screened Coulomb potential (SCP) while the quantum plasma has been treated under an exponential cosine screened Coulomb potential (ECSCP). Estimation of the spin orbit splitting under SCP and ECSCP plasma is restricted to the lowest two dipole allowed states while for the other two properties, the ground state as well as the first two excited states have been chosen. Calculations have been extended to nuclear charges for which appreciable relativistic corrections are noted. In all cases calculations have been extended up to such screening parameters for which the respective excitation energies tend towards their stability limit determined by the ionisation potential at that screening parameter. Interesting behavior of the respective properties with respect to the plasma coupling strength has been noted.
TL;DR: In this article, an analytic model for the electrostatic Debye layer formed at a plasma-liquid interface was constructed by combining the Gouy-Chapman theory for the liquid with a simple parabolic band model of the plasma sheath.
Abstract: We construct an analytic model for the electrostatic Debye layer formed at a plasma-liquid interface by combining the Gouy-Chapman theory for the liquid with a simple parabolic band model for the plasma sheath. The model predicts a nonlinear scaling between the plasma current density and the solution ionic strength, and we confirmed this behavior with measurements using a liquid-anode plasma. Plots of the measured current density as a function of ionic strength collapse the data and curve fits yield a plasma electron density of ∼10^{19}m^{-3} and an electric field of ∼10^{4}V/m on the liquid side of the interface. Because our theory is based firmly on fundamental physics, we believe it can be widely applied to many emerging technologies involving the interaction of low-temperature, nonequilibrium plasma with aqueous media, including plasma medicine and various plasma chemical synthesis techniques.
TL;DR: In this paper, a drift-diffusion model was proposed to account for both charge transport and ion vacancy motion in planar metal halide perovskite solar cells, where the slow ion dynamic was replaced by interfacial capacitances.
Abstract: Increasing evidence suggests that the presence of mobile ions in perovskite solar cells can cause a current-voltage curve hysteresis. Steady state and transient current-voltage characteristics of a planar metal halide CH$_3$NH$_3$PbI$_3$ perovskite solar cell are analysed with a drift-diffusion model that accounts for both charge transport and ion vacancy motion. The high ion vacancy density within the perovskite layer gives rise to narrow Debye layers (typical width $\sim$2nm), adjacent to the interfaces with the transport layers, over which large drops in the electric potential occur and in which significant charge is stored. Large disparities between (I) the width of the Debye layers and that of the perovskite layer ($\sim$600nm) and (II) the ion vacancy density and the charge carrier densities motivate an asymptotic approach to solving the model, while the stiffness of the equations renders standard solution methods unreliable. We derive a simplified surface polarisation model in which the slow ion dynamic are replaced by interfacial (nonlinear) capacitances at the perovskite interfaces. Favourable comparison is made between the results of the asymptotic approach and numerical solutions for a realistic cell over a wide range of operating conditions of practical interest.
TL;DR: In this paper, the first-principles VASP code was used to analyze the elastic properties of the KTaO3 and KNbO3 lattice parameters.
Abstract: Cubic KNbO3 and KTaO3 crystals are studied using the first-principles VASP code. By employing local density approximation (LDA), GGA-PBE, and HSE06, the lattice parameters are optimized and compared with available experimental data, and the best agreement is achieved with HSE06. Electronic structures such as density of states, band structures, and charge-density distribution are discussed in detail for both crystals. The single-crystal elastic constants, polycrystalline elastic modulus, compressibility, Poisson's ratio, and anisotropy factors are obtained from the Voigt–Reuss–Hill approximation. The elastic anisotropy is modeled and visualized in the light of the elastic properties of both systems. The bandgaps of the two crystals are calculated with LDA, PBE, HSE06, and GW approximations (GW0), and the results of HSE06 and GW0 agree well with experimental data. Then the more reliable optical properties of KNbO3 and KTaO3 are acquired based on the bandgaps with HSE06, in which the previous scissors operator correction is avoided. Both crystals are brittle, and KTaO3 exhibits higher hardness and stiffness than KNbO3. Some novel results, such as Debye temperatures, sound velocities, and the extreme values of Young's modulus are obtained.
Journal Article•
TL;DR: An analytic model for the electrostatic Debye layer formed at a plasma-liquid interface is constructed by combining the Gouy-Chapman theory for the liquid with a simple parabolic band model forThe plasma sheath, and it predicts a nonlinear scaling between the plasma current density and the solution ionic strength.
Abstract: We construct an analytic model for the electrostatic Debye layer formed at a plasma-liquid interface by combining the Gouy-Chapman theory for the liquid with a simple parabolic band model for the plasma sheath. The model predicts a nonlinear scaling between the plasma current density and the solution ionic strength, and we confirmed this behavior with measurements using a liquid-anode plasma. Plots of the measured current density as a function of ionic strength collapse the data and curve fits yield a plasma electron density of ∼10^{19}m^{-3} and an electric field of ∼10^{4}V/m on the liquid side of the interface. Because our theory is based firmly on fundamental physics, we believe it can be widely applied to many emerging technologies involving the interaction of low-temperature, nonequilibrium plasma with aqueous media, including plasma medicine and various plasma chemical synthesis techniques.
TL;DR: Lerner et al. as discussed by the authors compute the dielectric response of glasses starting from a microscopic system-bath Hamiltonian of the Zwanzig-Caldeira-Leggett type and using an ansatz from kinetic theory for the memory function in the resulting generalized Langevin equation.
Abstract: We compute the dielectric response of glasses starting from a microscopic system-bath Hamiltonian of the Zwanzig-Caldeira-Leggett type and using an ansatz from kinetic theory for the memory function in the resulting generalized Langevin equation. The resulting framework requires the knowledge of the vibrational density of states (DOS) as input, which we take from numerical evaluation of a marginally stable harmonic disordered lattice, featuring a strong boson peak (excess of soft modes over Debye ∼ω_{p}^{2} law). The dielectric function calculated based on this ansatz is compared with experimental data for the paradigmatic case of glycerol at T≲T_{g}. Good agreement is found for both the reactive (real) part of the response and for the α-relaxation peak in the imaginary part, with a significant improvement over earlier theoretical approaches. On the low-frequency side of the α peak, the fitting supports the presence of ∼ω_{p}^{4} modes at vanishing eigenfrequency as recently shown [E. Lerner, G. During, and E. Bouchbinder, Phys. Rev. Lett. 117, 035501 (2016)PRLTAO0031-900710.1103/PhysRevLett.117.035501]. α-wing asymmetry and stretched-exponential behavior are recovered by our framework, which shows that these features are, to a large extent, caused by the soft boson-peak modes in the DOS.
TL;DR: In this paper, the dielectric relaxation behavior of four polar molecules namely 2-Nitroaniline, 4-Bromoaniline and 4-Chlorophenol were studied in dilute solutions of benzene using microwave bench at 9.59 GHz frequency.
TL;DR: Based on measured electrical and optical parameters, a model to describe such parameters extracted with a global optimisation method, namely, particle swarm optimisation, agrees well with the measured data.
Abstract: This paper focuses on the analysis of cultivated collagen samples at the terahertz (THz) band using double debye model parameter extraction. Based on measured electrical and optical parameters, we propose a model to describe such parameters extracted with a global optimisation method, namely, particle swarm optimisation. Comparing the measured data with ones in the open literature, it is evident that using only cultivated collagen is not sufficient to represent the performance of the epidermis layer of the skin tissue at the THz band of interest. The results show that the differences between the measured data and published ones are as high as 14 and 6 for the real and imaginary values of the dielectric constant, respectively. Our proposed double debye model agrees well with the measured data.
TL;DR: In this article, the authors investigate the reconstruction behavior of the main spectral induced polarisation parameters across a two-dimensional complex resistivity imaging plane by considering a local anomalous polarisable body at different depths.
Abstract: Complex resistivity imaging provides information on the subsurface distribution of the electrical
conduction and polarisation properties. Spectral induced polarisation (SIP) refers to the frequency
dependence of these complex resistivity values. Measured SIP signatures are commonly analysed
by performing a Cole–Cole model fit or a Debye decomposition, yielding in particular chargeability
and relaxation time values. Given the close relation of these parameters with petrophysical
properties of relevance in various hydrogeological and environmental applications, it is crucial to
understand how well they can be reconstructed from multi-frequency complex resistivity imaging
with subsequent Cole–Cole or Debye decomposition analysis. In this work, we investigate, in a
series of numerical simulations, the reconstruction behaviour of the main spectral induced polarisation
parameters across a two-dimensional complex resistivity imaging plane by considering a local
anomalous polarisable body at different depths. The different anomaly positions correspond to different
cumulated sensitivity (coverage) values, which we find to be a simple and computationally
inexpensive proxy for resolution. Our results show that, for single-frequency measurements, the
reconstruction quality of resistivity and phase decreases strongly with decreasing cumulated sensitivity.
A similar behaviour is found for the recovery of Cole–Cole and Debye decomposition chargeabilities
from multi-frequency imaging results, while the reconstruction of the Cole–Cole exponent
shows non-uniform dependence over the examined sensitivity range. In contrast, the Cole–Cole and
Debye decomposition relaxation times are relatively well recovered over a broad sensitivity range.
Our results suggest that a quantitative interpretation of petrophysical properties derived from Cole–
Cole or Debye decomposition relaxation times is possible in an imaging framework, while any
parameter estimate derived from Cole–Cole or Debye decomposition chargeabilities must be used
with caution. These findings are of great importance for a successful quantitative application of
spectral induced polarisation imaging for improved subsurface characterisation, which is of interest
particularly in the fields of hydrogeophysics and biogeophysics.
TL;DR: In this article, an analytical expression of beam shape coefficients (BSCs) is derived using angular spectrum decomposition method (ASDM), and the scattering coefficients are expanded using Debye series (DSE) in order to isolate the contribution of single scattering process.
Abstract: The interaction of an axicon-generated vector Bessel beam (AGVBB) with a homogeneous sphere is investigated in the framework of generalized Lorenz-Mie theory (GLMT). An analytical expression of beam shape coefficients (BSCs) is derived using angular spectrum decomposition method (ASDM), and the scattering coefficients are expanded using Debye series (DSE) in order to isolate the contribution of single scattering process. The internal and near-surface electric fields are numerically analyzed, and the effect of beam location, polarization, order of beam, half-cone angle, and scattering process (namely Debye mode p) are mainly discussed. Numerical results show that a curve formed by extreme peaks can be observed, and the electric fields can be locally enhanced after the interaction of AGVBBs with the particle. Internal and near-surface fields, especially its local enhancement, are very sensitive to the beam parameters, including polarization, order, half-cone angle, etc. The internal fields can also be enhanced by various scattering process (or Debye mode p). Such results have important applications in various fields, including particle sizing, optical tweezers, etc.
TL;DR: In this article, the phonon and carrier thermal conductivities of thermoelectric materials were calculated using the Wiedemann-Franz law, Boltzmann equation, and a method called the Debye specific heat method.
Abstract: The phonon and carrier thermal conductivities of thermoelectric materials were calculated using the Wiedemann–Franz law, Boltzmann equation, and a method we propose in this study called the Debye specific heat method. We prepared polycrystalline n-type doped bismuth telluride (BiTe) and bismuth antimony (BiSb) bulk alloy samples and measured six parameters (Seebeck coefficient, resistivity, thermal conductivity, thermal diffusivity, magneto-resistivity, and Hall coefficient). The carrier density and mobility were estimated for calculating the carrier thermal conductivity by using the Boltzmann equation. In the Debye specific heat method, the phonon thermal diffusivity, and thermal conductivity were calculated from the temperature dependence of the effective specific heat by using not only the measured thermal conductivity and Debye model, but also the measured thermal diffusivity. The carrier thermal conductivity was also evaluated from the phonon thermal conductivity by using the specific heat. The ratio of carrier thermal conductivity to thermal conductivity was evaluated for the BiTe and BiSb samples, and the values obtained using the Debye specific heat method at 300 K were 52% for BiTe and <5.5% for BiSb. These values are either considerably larger or smaller than those obtained using other methods. The Dulong–Petit law was applied to validate the Debye specific heat method at 300 K, which is significantly greater than the Debye temperature of the BiTe and BiSb samples, and it was confirmed that the phonon specific heat at 300 K has been accurately reproduced using our proposed method.
TL;DR: The present results compare well for a lower range of the applied electric field and surface charge density with the existing results for a perfectly dielectric particle with a hydrophobic surface based on the first-order perturbation analysis due to Khair and Squires.
Abstract: We consider the electrophoresis of a charged colloid for a generalized situation in which the particle is considered to be polarizable and the surface exhibits hydrophobicity. The dielectric polarization of the particle creates a nonlinear dependence of the electrophoretic velocity on the applied electric field, and the core hydrophobicity amplifies the fluid convection in the Debye layer. Thus, a linear analysis is no longer applicable for this situation. The present analysis is based on the numerical solution of the nonlinear electrokinetic equations based on the Navier-Stokes-Nernst-Planck-Poisson equations coupled with the Laplace equation for the electric field within the dielectric particle. The hydrophobicity of the particle may influence its electric polarization by enhancing the convective transport of ions. The nonlinear effects, such as double-layer polarization and relaxation, are also influenced by the hydrophobicity of the particle surface. The present results compare well for a lower range of the applied electric field and surface charge density with the existing results for a perfectly dielectric particle with a hydrophobic surface based on the first-order perturbation analysis due to Khair and Squires [Phys. Fluids 21, 042001 (2009)PHFLE61070-663110.1063/1.3116664]. Dielectric polarization creates a reduction in particle electrophoretic velocity, and its impact is strong for a moderate range of Debye length. A quantitative measure of the nonlinear effects is demonstrated by comparing the electrophoretic velocity with an existing linear model.
TL;DR: Schwerdtfeger and Hermann as mentioned in this paper showed that the phase transition from fcc to hcp cannot account for the large discrepancies observed in the high-pressure regime of argon.
Abstract: The equation of state $P(V,T)$ for solid argon is determined by the calculation of accurate static and vibrational terms in the free energy. The static component comes from a quantum theoretical many-body expansion summing over all energetic contributions from two-, three-, and four-body fragments treated with relativistic coupled cluster theory, while the lattice vibrations are described at an anharmonic level including two- and three-body forces as well as temperature effects. The dynamic part is calculated within the Debye and Einstein approximation, as well as by a more accurate phonon treatment where the vibrational motions in the lattice are coupled. Our results are in good agreement with room-temperature high-pressure experimental data up to $\ensuremath{\sim}20$ GPa. In the 20--100 GPa pressure range, however, we see considerable deviations between experiment and theory, perhaps indicating missing four-body contributions (beyond the quadruple dipole terms included here), missing five and higher-body effects, and the need to go beyond the coupled cluster singles-doubles with perturbative triples treatment in such higher-body forces. This contrasts with the results for solid neon, where excellent agreement has been achieved taking only two- and three-body forces into account [P. Schwerdtfeger and A. Hermann, Phys. Rev. B 80, 064106 (2009)]. We demonstrate that the phase transition from fcc to hcp cannot account for the large discrepancies observed. Density functional calculations give very mixed results in the high-pressure region, but some functionals such as optB88-vdW (proposed by Lundqvist and co-workers) describe the many-body forces in argon reasonably well over the range of pressures investigated. Theoretical investigations of the heavier rare gas solids reaching experimental accuracy in the high-pressure regime therefore remain a significant challenge.
TL;DR: For highly non-instantaneous response, it theoretically find a decelerating Airy pulse is still transformed into Airy wave packet with deceleration, and the theoretical predictions are confirmed by numerical simulations.
Abstract: The propagation of decelerating Airy pulses in non-instantaneous cubic medium is investigated both theoretically and numerically. In a Debye model, at variance with the case of accelerating Airy and Gaussian pulses, a decelerating Airy pulse evolves into a single soliton for weak and general non-instantaneous response. Airy pulses can hence be used to control soliton generation by temporal shaping. The effect is critically dependent on the response time, and could be used as a way to measure the Debye type response function. For highly non-instantaneous response, we theoretically find a decelerating Airy pulse is still transformed into Airy wave packet with deceleration. The theoretical predictions are confirmed by numerical simulations.
TL;DR: In this article, Debye-Waller factors presented in terms of cumulant expansion up to the third order, thermal expansion coefficient, X-ray absorption fine structure (XAFS) spectra and their Fourier transform magnitudes of Zn (hcp crystal) have been calculated and measured.
Abstract: Debye-Waller factors presented in terms of cumulant expansion up to the third order, thermal expansion coefficient, X-ray absorption fine structure (XAFS) spectra and their Fourier transform magnitudes of Zn (hcp crystal) have been calculated and measured. The results have been obtained based on the quantum statistically derived method using that the calculations and measurements are necessary only for the second cumulants from which all other XAFS parameters have been provided. The many-body effects included in the present one-dimensional model are taken into account based on the first shell near neighbor contributions to the vibration between absorber and backscaterer atoms. Morse potential is assumed to describe the single-pair atomic interaction included in the anharmonic interatomic effective potential. Numerical results for Zn are found to be in good agreement with the obtained experimental data which show evident temperature dependence of the thermodynamic properties, anharmonic effects and structural parameters of the material.
TL;DR: In this article, the sensing ability of pure C24, C32, C60, B-, and AlC59 nano-cages toward the CNCl molecule using DFT calculations was studied.
Abstract: Here, we studied the sensing ability of pure C24, C32, C60, B-, and AlC59 nano-cages toward the CNCl molecule using DFT calculations Noticeably, the adsorption energies of CNCl–AlC59 and ClCN–BC59 with–1174 and–0382 eV which were more than other adsorption configurations (C24, C32, C60) standing for higher detection of these systems On the other hand, concerning dipole change detection, the CNCl–AlC59 and ClCN–BC59 were recognized as the most promising sensor systems introduced at the present study with the dipole moment values of 1387 and 1017 Debye The recovery time for all adsorption configurations were negligible
TL;DR: A one-dimensional, two-fluid, steady state model used for the analysis of ion temperature effects to the plasma-wall transition is used and it is concluded that larger ion temperature results in a better shielding of the plasma from the wall.
Abstract: A one-dimensional, two-fluid, steady state model is used for the analysis of ion temperature effects to the plasma-wall transition. In this paper, the model is solved for a finite ratio e between the Debye and the ionization length, while in Part II [T. Gyergyek and J. Kovacic, Phys Plasmas 24, 063506 (2017)], the solutions for e = 0 are presented. Ion temperature is treated as a given, independent parameter and it is included in the model as a boundary condition. It is shown that when the ion temperature larger than zero is selected, the ion flow velocity and the electric field at the boundary must be consistent with the selected ion temperature. A numerical procedure, how to determine such “consistent boundary conditions,” is proposed, and a simple relation between the ion temperature and ion velocity at the boundary of the system is found. The effects of the ion temperature to the pre-sheath length, potential, ion temperature, and ion density drops in the pre-sheath and in the sheath are investigated. ...