Showing papers on "Debye published in 2020"
TL;DR: In this article, the structural properties of double layered perovskite Ba22+Sm3+Nb5+O62− were explored based on the structural optimization, including elasto-mechanical, thermoelectric, and thermodynamics.
42 citations
41 citations
Posted Content•
TL;DR: In this article, all the existing master equations for quarkonium are systematically rederived as Lindblad equations in a uniform framework and the quantum Brownian motion of heavy quark pair in the QGP is studied in detail.
Abstract: Dissociation of quarkonium in quark-gluon plasma (QGP) is a long standing topic in relativistic heavy-ion collisions because it signals one of the fundamental natures of the QGP -- Debye screening due to the liberation of color degrees of freedom. Among recent new theoretical developments is the application of open quantum system framework to quarkonium in the QGP. Open system approach enables us to describe how dynamical as well as static properties of QGP influences the time evolution of quarkonium.
Currently, there are several master equations for quarkonium corresponding to various scale assumptions, each derived in different theoretical frameworks. In this review, all of the existing master equations are systematically rederived as Lindblad equations in a uniform framework. Also, as one of the most relevant descriptions in relativistic heavy-ion collisions, quantum Brownian motion of heavy quark pair in the QGP is studied in detail. The quantum Brownian motion is parametrized by a few fundamental quantities of QGP such as real and imaginary parts of heavy quark potential (complex potential), heavy quark momentum diffusion constant, and thermal dipole self-energy constant. This indicates that the yields of quarkonia such as $J/\psi$ and $\Upsilon$ in the relativistic heavy-ion collisions have the potential to determine these fundamental quantities.
40 citations
TL;DR: Wang et al. as mentioned in this paper presented analysis of more than 100 large-amplitude bipolar electrostatic structures in a quasi-perpendicular supercritical Earth's bow shock crossing, measured by the Magnetospheric Multiscale spacecraft.
Abstract: Author(s): Wang, R; Vasko, IY; Mozer, FS; Bale, SD; Artemyev, AV; Bonnell, JW; Ergun, R; Giles, B; Lindqvist, PA; Russell, CT; Strangeway, R | Abstract: We present analysis of more than 100 large-amplitude bipolar electrostatic structures in a quasi-perpendicular supercritical Earth's bow shock crossing, measured by the Magnetospheric Multiscale spacecraft. The occurrence of the bipolar structures is shown to be tightly correlated with magnetic field gradients in the shock transition region. The bipolar structures have negative electrostatic potentials and spatial scales of a few Debye lengths. The bipolar structures propagate highly oblique to the shock normal with velocities (in the plasma rest frame) of the order of the ion-acoustic velocity. We argue that the bipolar structures are ion phase space holes produced by the two-stream instability between incoming and reflected ions. This is the first identification of the ion two-stream instability in collisionless shocks.
34 citations
TL;DR: The findings about the coupling of Brownian and Néel process and the effective relaxation time provide an important theoretical insight that will have also important consequences for the interpretation of magnetic susceptibility measurements and magnetorelaxometry analysis.
Abstract: The intriguing properties of magnetic nanoparticles have sparked a growing number of theoretical studies as well as practical applications. Here, we provide the first comprehensive study of the influence of interactions on the two main relaxation mechanisms: internal (Neel) and Brownian relaxation. While non-interacting magnetic nanoparticles show Debye behavior with an effective relaxation time, many authors use this model also for the interacting case. Since Neel relaxation is typically a thermally activated process on times scales that are many orders of magnitude larger than the underlying micromagnetic times, we use extensive computer simulations employing a Brownian dynamics/Monte-Carlo algorithm to show that dipolar interactions lead to significant deviations from the Debye behavior. We find that Neel and Brownian relaxation can be considered as independent processes for short enough times until dipolar interactions lead to a coupling of these mechanisms, making the interpretation more difficult. We provide mean-field arguments that describe these short and long-time, effective relaxation times well for weak up to moderate interaction strengths. Our findings about the coupling of Brownian and Neel process and the effective relaxation time provide an important theoretical insight that will have also important consequences for the interpretation of magnetic susceptibility measurements and magnetorelaxometry analysis.
33 citations
TL;DR: In this paper, a hybrid perovskite (C3H7NH3PbI3) was successfully synthesized by a solgel technique and its structural, optical, and dielectric properties have been studied in detail.
Abstract: Propylammonium lead iodide (C3H7NH3PbI3), a promising hybrid perovskite, is successfully synthesized by a solgel technique. Structural, optical, and dielectric properties have been studied in detail. The dielectric constant, loss factor, electric modulus, and AC and DC conductivity of this hybrid perovskite exhibit strong temperature dependence over the frequency range of 10 Hz ≤ f ≤ 8 MHz. The Nyquist plot reveals the distinct contributions of grain and grain boundary to the total impedance. The dielectric constant is found to increase with temperature in the high frequency region. The modified Cole–Cole plot shows that the space charge and free charge conductivity increase with the elevation of temperature, whereas the relaxation time decreases with the rise in temperature. From the modified Kohlrausch–Williams–Watts equation, we perceived asymmetrical nature in electric modulus spectra at various temperatures, which corresponds to the non-Debye type nature of perovskite. It has also been found that, with the elevation of temperature, the imaginary part of electric modulus spectra shifts from the non-Debye type toward the Debye type nature, though failing to acquire exact Debye type response, and emerges as a semiconductor material. AC conductivity of PAPbI3 is illustrated on the basis of the correlated barrier hopping (CBH) mechanism. Activation energy estimated from both modulus spectra and DC conductivity matches well, affirming the similarity between relaxation behavior and conduction mechanism. Along with all these, PAPbI3 possesses a high dielectric constant associated with a small dielectric loss, making it a potential candidate for energy harvesting devices.
33 citations
05 Dec 2020
TL;DR: In this article, a class of Yukawa potential is adopted as the quark-antiquark interaction potential for studying the mass spectra of heavy mesons, and the potential was made to be temperature-dependent by replacing the screening parameter with Debye mass.
Abstract: A class of Yukawa potential is adopted as the quark-antiquark interaction potential for studying the mass spectra of heavy mesons. The potential was made to be temperature-dependent by replacing the screening parameter with Debye mass. We solved the radial Schrodinger equation analytically using the series expansion method and obtained the energy eigenvalues. The present results are applied for calculating the mass spectra of heavy mesons such as charmonium and bottomonium . Two special cases were considered when some of the potential parameters were set to zero, resulting into Hellmann potential, and Coulomb potential, respectively. The present potential provides satisfying results in comparison with experimental data and the work of other researchers.
32 citations
TL;DR: In this article, the authors show that dipole-dipole correlations give rise to an additional process in the dielectric spectrum slightly slower than the α relaxation, which renders the resulting combined peak narrower than observed by other experimental techniques.
Abstract: The nonexponential shape of the α process observed in supercooled liquids is considered as one of the hallmarks of glassy dynamics and has thus been under study for decades, but is still poorly understood. For a polar van der Waals liquid, we show here-in line with a recent theory-that dipole-dipole correlations give rise to an additional process in the dielectric spectrum slightly slower than the α relaxation, which renders the resulting combined peak narrower than observed by other experimental techniques. This is reminiscent of the Debye-process found in monohydroxy alcohols. The additional peak can be suppressed by weakening the dipole-dipole interaction via dilution with a nonpolar solvent.
31 citations
TL;DR: The dielectric properties of six refined edible oils with different fatty-acid compositions were determined for oils incubated at 180 °C up to 40 h and the specific refraction, specific polarization, orientation polarization, and dipole moment were determined using Lorenz–Lorentz, Debye and Onsager relationship.
Abstract: The dielectric properties of six refined edible oils with different fatty-acid compositions were determined for oils incubated at 180 °C up to 40 h. The oil degradation was evaluated by the dielectric dispersion and dielectric loss in the frequency range from 40 Hz to 2 MHz at 25 °C, refractive index, density, saponification number, and specific absorption coefficient at 232 and 268 nm. The dependence of the dielectric properties on frequency has been evaluated with Corach, Cole–Cole, and the universal power law models, giving the novel strategies for the interpretation of the dielectric spectra of thermally treated oils. The derived parameters—the dielectric constant, the electrical conductivity, the relaxation time τ and the exponents α, p, and n—are discussed with respect to the increased oxidation evidenced by specific absorption coefficients and polar products, as measured by the dielectric constant of the thermally treated oils. The specific refraction, specific polarization, orientation polarization, and dipole moment were determined using Lorenz–Lorentz, Debye and Onsager relationship. All above parameters obtained increased during the thermal treatment, except specific refraction, the electrical conductivity and the relaxation time. The dielectric constant-macroscopic parameter was compared with microscopic parameter polarization and dipole moment; the linear dependence was found to be R 2 = 0.971 .
21 citations
TL;DR: The Debye mass sets a scale for the screening of static charges and the scattering of fast charges within a gauge plasma as discussed by the authors, inspired by its potential cosmological applications, determined a QCD Debye Mass at two-loop order in a broad temperature range (1 GeV--10 TeV).
Abstract: The Debye mass sets a scale for the screening of static charges and the scattering of fast charges within a gauge plasma. Inspired by its potential cosmological applications, we determine a QCD Debye mass at two-loop order in a broad temperature range (1 GeV--10 TeV), demonstrating how quark mass thresholds get smoothly crossed. Along the way, integration-by-parts identities pertinent to massive loops at finite temperature are illuminated.
19 citations
TL;DR: In this paper, the electric multipole polarizabilities of one-electron atoms embedded in weakly coupled Debye plasmas are calculated in the non-relativistic framework.
Abstract: The electric multipole polarizabilities of one-electron atoms embedded in weakly coupled Debye plasmas are calculated in the non-relativistic framework. The static dipole, quadrupole, octopole, and hexadecapole polarizabilities for hydrogen atoms in both ground and excited states at a variety of Debye screening parameters are calculated in high precision based on the sum-over-states method, where the system bound and continuum states are produced by employing the generalized pseudospectral method. It is shown that the contribution of bound states to the polarizability decreases with increasing the plasma screening strength, whereas the contribution of continuum states is enhanced. At very small screening parameters where the plasma environment starts to take effect, it is found that the 2 l -pole polarizability for s -wave states with principle quantum number n ≥ l + 1 has an abrupt change from its non-screening value to infinity. We attribute such a phenomenon to the sudden non-degeneracy of different angular momentum states in the n shell. With continuously increasing the screening strength, the polarizabilities for n ≥ l + 1 states decrease to certain values and, eventually, they approach to infinity at the critical screening parameter. For states with n ≤ l, the 2 l -pole polarizabilities show regular enhancement from the non-screening value to infinity. The present results are compared with other theoretical calculations available in the literature and it is shown that our work has established by now the most accurate predictions of multipole oscillator strengths and polarizabilities for one-electron atoms in Debye plasmas.
TL;DR: The case is made that the large errors found only for small molecules in the gas phase and weak solvents cannot be expected to improve via the optimal tuning procedure, which enforces a condition that is exact only in the well-separated donor-acceptor limit, and the utility of the optimally tuned density functional approach is demonstrated.
Abstract: Electronically excited states characterized by intramolecular charge transfer play an essential role in many biological processes and optical devices. The ability to make quantitative ab initio predictions of the relative energetics involved is a challenging yet desirable goal, especially for large molecules in solution. In this work, we present a data set of 61 experimental measurements of absorption and emission processes, both in the gas phase and in solvents representing a broad range of polarities, which involve intramolecular charge transfer mediated by a nonzero, "twisted" dihedral angle between one or more donor and acceptor subunits. Among a variety of density functionals investigated within the framework of linear-response theory, the "optimally tuned" LRC-ωPBE functional, which utilizes a system-specific yet nonempirical procedure to specify the range-separation parameter, emerges as the preferred choice. For the entire set of excitation energies, involving changes in dipole moment ranging from 4 to >20 Debye, the mean signed and absolute errors are 0.02 and 0.18 eV, respectively (compared, e.g., to -0.30 and 0.30 for PBE0, 0.44 and 0.47 for LRC-ωPBEh, 0.83 and 0.83 for ωB97X-V). We analyze the performance of polarizable continuum solvation models available in Q-Chem that partition the solvent response into fast and slow time scales, and clear trends emerge when measurements corresponding to the four small 4-(dimethylamino)benzonitrile (DMABN)-like molecules and a charged species are excluded. We make the case that the large errors found only for small molecules in the gas phase and weak solvents cannot be expected to improve via the optimal tuning procedure, which enforces a condition that is exact only in the well-separated donor-acceptor limit, and present empirical evidence implicating the outsized importance for small donor-acceptor systems of relaxation effects that cannot be accounted for by the linear-response time-dependent density functional theory within the adiabatic approximation. Finally, we demonstrate the utility of the optimally tuned density functional approach by targeting the charge-transfer states of a large biomimetic model system for light-harvesting structures in Photosystem II.
TL;DR: In this article, the interpretation of the RVM test requires expertise and if the transformer presents a high interfacial polarization it is not possible to diagnose it in detail, therefore, the Debye model is proposed in this work for enhancing RVM interpretation.
Abstract: The aim of this document is to present how the interpretation of the RVM (Recovery Voltage Measurement) test can be improved through the use of a Debye equivalent circuit. As it is described in the literature, the interpretation of the RVM test requires expertise and if the transformer presents a high interfacial polarization it is not possible to diagnose it in detail. The Debye model is proposed in this work for enhancing RVM interpretation. This model is based on an electrical circuit that includes basic R-C components, that allows two interesting features: on one hand, insulation physical effects can be separately represented and, on the other, the values of the R-C components can be calculated from the RVM response. A method is proposed in which using a sweep with a constant number of predefined time constants branches allows us to determine the areas of influence of the different compounds present in the dielectric. Finally, several case studies are presented, in which it is correlated a dielectric oil treatment carried out and the equivalent circuit changes using a sweep allows us to analyze different branches’ sensitivity and to identify the areas of influence of each compound.
TL;DR: In this article, a novel mechanism of microwave absorption in superconductors, which is similar to the Debye absorption mechanism in molecular gases, is discussed, and the contribution of this mechanism to the ac conductivity is proportional to the inelastic quasiparticle relaxation time.
Abstract: We discuss a novel mechanism of microwave absorption in superconductors, which is similar to the Debye absorption mechanism in molecular gases. The contribution of this mechanism to the ac conductivity is proportional to the inelastic quasiparticle relaxation time ${\ensuremath{\tau}}_{\mathrm{in}}$ rather than the elastic one ${\ensuremath{\tau}}_{\mathrm{el}}$ and therefore it can be much larger than the conventional one. The Debye contribution to the linear conductivity arises only in the presence of a dc supercurrent in the system and its magnitude depends strongly on the orientation of the microwave field relative to the supercurrent. The Debye contribution to the nonlinear conductivity exists even in the absence of dc supercurrent, and it is proportional to ${\ensuremath{\tau}}_{\mathrm{in}}$. Therefore the nonlinear threshold is anomalously low. Microwave absorption measurements may provide direct information about ${\ensuremath{\tau}}_{\mathrm{in}}$ in superconductors.
TL;DR: In this paper, the authors derived the Dresselhaus spin-orbit coupling that is generated by this transition dipole for heavy holes in an asymmetric quantum well, which is important for understanding the origin of spin splitting in quantum wells, spin coherence/relaxation, spin resonance, and spin nonconserving tunneling in double quantum dot systems.
Abstract: In the envelope-function approximation, interband transitions produced by electric fields are neglected. However, electric fields may lead to a spatially local $(k\text{\ensuremath{-}}\mathrm{independent})$ coupling of band (internal, pseudospin) degrees of freedom. Such a coupling exists between heavy-hole and light-hole (pseudo)spin states in III-V semiconductors, such as GaAs, or in group IV semiconductors (germanium, silicon,...) with broken inversion symmetry. Here, we calculate the electric-dipole (pseudospin-electric) coupling for holes in GaAs from first principles. We find a transition dipole of 0.5 debye, a significant fraction of that for the hydrogen-atom $1s\ensuremath{\rightarrow}2p$ transition. In addition, we derive the Dresselhaus spin-orbit coupling that is generated by this transition dipole for heavy holes in an asymmetric quantum well. A quantitative microscopic description of this pseudospin-electric coupling may be important for understanding the origin of spin splitting in quantum wells, spin coherence/relaxation $({T}_{2}^{*}/{T}_{1})$ times, spin-electric coupling for cavity-QED, electric-dipole spin resonance, and spin nonconserving tunneling in double quantum dot systems.
02 Jan 2020
TL;DR: In this paper, it was shown that a strong boson peak anomaly in the vibrational density of states (VDOS) can be due almost entirely to the presence of low-energy optical phonons, provided that their energy is comparable to that of the acoustic modes at the Brillouin zone boundary.
Abstract: It is widely accepted that structural glasses and disordered crystals exhibit anomalies in the their thermal, mechanical and acoustic properties as manifestations of the breakdown of the long-wavelength approximation in a disordered dissipative environment. However, the same type of glassy-like anomalies (i.e. boson peak in the vibrational density of states (VDOS) above the Debye level, peak in the normalized specific heat at $T\simeq10 K$ etc) have been recently observed also in perfectly ordered crystals, including thermoelectric compounds. Here we present a theory that predicts these surprising effects in perfectly ordered crystals as a result of low-lying (soft) optical phonons. In particular, it is seen that a strong boson peak anomaly (low-energy excess of modes) in the VDOS can be due almost entirely to the presence of low-energy optical phonons, provided that their energy is comparable to that of the acoustic modes at the Brillouin zone boundary. The boson peak is predicted also to occur in the heat capacity at low $T$. In presence of strong damping (which might be due to anharmonicities in the ordered crystals), these optical phonons contribute to the low-$T$ deviation from Debye's $T^{3}$ law, producing a linear-in-$T$ behavior which is typical of glasses, even though no assumptions of disorder whatsoever are made in the model. These findings are relevant for understanding and tuning thermal transport properties of thermoelectric compounds, and possibly for the enhancement of electron-phonon superconductivity.
TL;DR: In this article, it was found that change in the functionality of the H-bonding moiety influences the architecture of the supramolecular nanoassemblies, and not the strength of hydrogen bonds itself, but the diverse population of nanoassociates, their size, and the spatial organization of the molecules in clusters have a strong influence on the appearance/absence as well as the intensity of the Debye relaxation.
Abstract: Infrared and dielectric spectroscopy, X-ray diffraction, and density functional theory computations have been used to study the hydrogen-bonding pattern, molecular dynamics, internal structure, and dipole moment distribution in 2-ethyl-1-hexanol, 2-ethyl-1-hexylamine, 2-ethyl-1-hexanethiol, and 1-phenyl-2-butanol. Dielectric investigations revealed that Kirkwood–Frohlich correlation factor is much larger or lower than the unity in the vicinity of the glass transition, dependent on the compound. It indicates that change in the functionality of the H-bonding moiety influences the architecture of the supramolecular nanoassemblies. Further thorough experimental and theoretical considerations confirmed this hypothesis. Moreover, it was found that not the strength of hydrogen bonds itself, but the diverse population of nanoassociates, their size, and the spatial organization of the molecules in clusters have a strong influence on the appearance/absence as well as the intensity of the Debye relaxation. The resul...
TL;DR: The proposed DUGKS becomes an asymptotic preserving scheme, which automatically degenerates to be consistent with the discretization of corresponding limiting models, which provides an easy-to-implement and efficient way for the investigation of electrical potential in all normalized Debye regimes.
TL;DR: The experimental results suggest that the Debye process in monoalcohols is an entropic process manifested by the total dipole fluctuation of the supramolecular structures, which is triggered and driven by the relaxation.
Abstract: The dynamics and thermodynamics of the Debye and structural (α) relaxations in isomeric monoalcohols near the glass transition temperature Tg are explored using dielectric and calorimetric techniques. The α relaxation strength at Tg is found to correlate with the heat capacity increment, but no thermal signals can be detected to link to the Debye relaxation. We also observed that the activation energy of the Debye relaxation in monoalcohols is quantitatively correlated with that of the α relaxation at the kinetic Tg, sharing the dynamic behavior of the Rouse modes found in polymers. The experimental results together with the analogy to the Rouse modes in polymers suggest that the Debye process in monoalcohols is an entropic process manifested by the total dipole fluctuation of the supramolecular structures, which is triggered and driven by the α relaxation.
TL;DR: In this article, low-energy ions are difficult to measure, mainly due to spacecraft charging, and the ions are attracted to or repelled from the charged surface prior to detection, which changes both the energy and tra...
Abstract: Low-energy ions are difficult to measure, mainly due to spacecraft charging. The ions are attracted to or repelled from the charged surface prior to detection, which changes both the energy and tra ...
TL;DR: This paper generates Debye random media in two dimensions using an accelerated Yeong-Torquato construction algorithm and ascertains microstructural descriptors of the constructed media, including their surface correlation functions, pore-size distributions, lineal-path function, and chord-length probability density function.
Abstract: In their seminal paper on scattering by an inhomogeneous solid, Debye and coworkers proposed a simple exponentially decaying function for the two-point correlation function of an idealized class of two-phase random media. Such Debye random media, which have been shown to be realizable, are singularly distinct from all other models of two-phase media in that they are entirely defined by their one- and two-point correlation functions. To our knowledge, there has been no determination of other microstructural descriptors of Debye random media. In this paper, we generate Debye random media in two dimensions using an accelerated Yeong-Torquato construction algorithm. We then ascertain microstructural descriptors of the constructed media, including their surface correlation functions, pore-size distributions, lineal-path function, and chord-length probability density function. Accurate semianalytic and empirical formulas for these descriptors are devised. We compare our results for Debye random media to those of other popular models (overlapping disks and equilibrium hard disks) and find that the former model possesses a wider spectrum of hole sizes, including a substantial fraction of large holes. Our algorithm can be applied to generate other models defined by their two-point correlation functions, and their other microstructural descriptors can be determined and analyzed by the procedures laid out here.
DOI•
23 Apr 2020
TL;DR: In this paper, the authors analyze the dimensionally reduced theories of high-temperature QCD, namely electrostatic and magnetostatic QCDs, and determine another low-energy coefficient in elec-trostatic QCD.
Abstract: Matter alters its properties remarkably when confronted with extreme conditions such astemperatures as high as in the early universe. The emergenceof the Quark-Gluon Plasma andrestoration of electroweak symmetry through phase transitions are but the most prominentphenomena to invigorate studies of gauge theories at finite temperatures. If the temperatureis sufficiently high, static observables are effectively described in a reduced dimension by aframework known as Dimensional Reduction.The computer algebraic multi-loop treatment of perturbation theory for finite-temperaturetheories is at the core of this thesis. It adopts sophisticated tools from zero temperature todecimate typically vast numbers of Feynman integrals with the objective to automate thedimensional reduction. To accomplish this, integration-by-parts identities pertinent to bothmassless and massive loops at finite temperature are illuminated. Additionally, an inclusionof higher-dimensional operators in these theories is first motivated and then generalised.The developed tools are applied to review the advancements of [1] in chapter 4 and [2] inchapter 5. There, we analyse the dimensionally reduced theories of high-temperature QCD,namely electrostatic and magnetostatic QCD.We inspect three-loop contributions stemming from non-static modes to the magnetostaticcoupling in dimensionally reduced hot Yang-Mills theory [1]. By including dimension-sixoperators the result is found to be infrared finite and influenced by all scales in the QCDhierarchy. Incorporating also electrostatic effects indicates a non-perturbative ultrasoft gaugecoupling atO(α3/2s).Based on its relevance in cosmology, we determine another low-energy coefficient in elec-trostatic QCD, the Debye mass. By including effects from massive fermions up to twoloops [2], energy ranges of (1 GeV–10 TeV) are scanned to showthe smooth crossing ofquark mass thresholds.
TL;DR: In this paper, the authors studied the Higgs mechanism and the Debye shielding for the Bopp-Podolsky theory of electrodynamics and found that not only the massless sector of the Podolsky Theory acquires a mass in both these phenomena, but also that its massive sector has its mass changed.
Abstract: In this work we study the Higgs mechanism and the Debye shielding for the Bopp–Podolsky theory of electrodynamics. We find that not only the massless sector of the Podolsky theory acquires a mass in both these phenomena, but also that its massive sector has its mass changed. Besides exploring the behavior of the screened potentials, we find a peculiar temperature [Formula: see text] associated with the Podolsky length.
TL;DR: The research examined the process of protein hydrolysis by a combination of absorption spectra and Debye analysis, and demonstrated that terahertz spectroscopy is a powerful technology for the investigation of biomolecular reactions, with potential applications in variety of fields.
TL;DR: The approach allows the description of metals with complicate dielectric function profiles in the frequency domain to be included in the TD-BEM framework and it has been used to investigate the time-dependent field acting locally close to nanoparticle vertices.
Abstract: Investigating nanoplasmonics in an explicit time-dependent perspective is a natural choice when light pulses are used and may also reveal aspects that are hidden in a frequency-based picture. In the past, we proposed a method time domain-boundary element method (TD-BEM) to simulate the time dependent polarization of nanoparticles based on a boundary element method that is particularly suitable to interface with a quantum atomistic description of nearby molecules. So far, however, metal dielectric functions in TD-BEM have been modeled through analytic expressions, such as those of Debye and Drude–Lorentz, which cannot account for multiple electronic resonances. Our approach allows us to include in the TD-BEM framework also the description of metals with complicate dielectric function profiles in the frequency domain. Particularly, among all metals, gold is a challenging case due to the presence of many transition frequencies. We applied our methods to different metals (gold, silver, and the less commonly investigated rhodium) and different shaped nanoparticles (spheres, ellipsoids, and cubes), the approach has been tested comparing TD-BEM and frequency domain BEM absorption spectra, and it has been used to investigate the time-dependent field acting locally close to nanoparticle vertices.
TL;DR: In this article, the dipole moment, energy gap and infrared spectrum of fullerene C70 molecule under external electric field (0, 0.040 atomic units) were studied with density functional theory at B3PW91/3-21G level.
Abstract: Fullerene C70 has a broad application prospect. It is of great significance for investigating the properties of fullerene C70 under the external electric field. The dipole moment, energy gap and infrared spectrum of fullerene C70 molecule under external electric field (0–0.040 atomic units) are studied with density functional theory at B3PW91/3-21G level. The dipole moment increases almost linearly from 0.005 to 65.005 Debye and the energy gap decreases continuously. The effect of external electric field on the infrared spectrum is great and it can be found that certain vibrational mode become active due to the symmetry reduction due to the external electric field. Meanwhile, the ultraviolet–visible absorption spectra, the excitation wavelength, the excitation energy, and oscillator strength of first fourteen excited states of fullerene C70 under the external electric field are also studied with the time-dependent density functional theory at B3PW91/3-21G level. It is found that the absorption peak of fullerene C70 occurs red shift from 504.78 to 736.39 nm. The excitation energy decreases rapidly and the excitation wavelength increases a lot with the external electric field. The results can offer an important reference to use external electric field to tune the properties of fullerene C70.
TL;DR: In this article, a waveguide with central frequency 868 MHz is used in the transmission/reflection operation regime to accurately measure the behavior of the complex permittivity of high-complex permittivities granular materials, and it has been frequency extended up to 3 GHz using the Debye fit relaxation model.
Abstract: A waveguide with central frequency 868 MHz is used in the transmission/reflection operation regime to accurately measure the behavior of the complex permittivity of high complex permittivity granular materials, and it has been frequency-extended up to 3 GHz using the Debye fit relaxation model. It is shown that for highly granular high permittivity materials, a waveguide-based transmission/reflection technique is necessary to reduce the uncertainty of the extracted permittivity values. The technique is first described and validated with isopropyl alcohol and then applied to the characterization of cement-based materials. This article provides accurate data on the evolution of the complex permittivity of concrete and mortar from the moment of pouring until air-dried condition is achieved.
Journal Article•
TL;DR: In this paper, it was found that not the strength of hydrogen bonds itself, but the diverse population of nanoassociates, their size, and the spatial organization of the molecules in clusters have a strong influence on the appearance/absence as well as the intensity of the Debye relaxation.
Abstract: Infrared and dielectric spectroscopy, X-ray diffraction, and density functional theory computations have been used to study the hydrogen-bonding pattern, molecular dynamics, internal structure, and dipole moment distribution in 2-ethyl-1-hexanol, 2-ethyl-1-hexylamine, 2-ethyl-1-hexanethiol, and 1-phenyl-2-butanol. Dielectric investigations revealed that Kirkwood–Frohlich correlation factor is much larger or lower than the unity in the vicinity of the glass transition, dependent on the compound. It indicates that change in the functionality of the H-bonding moiety influences the architecture of the supramolecular nanoassemblies. Further thorough experimental and theoretical considerations confirmed this hypothesis. Moreover, it was found that not the strength of hydrogen bonds itself, but the diverse population of nanoassociates, their size, and the spatial organization of the molecules in clusters have a strong influence on the appearance/absence as well as the intensity of the Debye relaxation. The results reported herein are of fundamental interest for a better understanding of the molecular origin of this characteristic process and impact of the molecular architecture, steric hindrance, and functionality on the nanoscale supramolecular assembling in various materials.
TL;DR: In this paper, a two-dimensional allotrope of the silicon nitrides family was found during the effort to construct a nanosheet from the unit cell of hexagonal β -Si3N4.
TL;DR: The temperature dependence of the crystallographic and thermoelastic properties of BaZrO3 perovskite in the temperature range 4.2 and 450 K was investigated using high-resolution time-of-flight neutron powder diffraction and literature values of the isobaric heat capacity as discussed by the authors.
Abstract: The temperature dependence of the crystallographic and thermoelastic properties of BaZrO3 perovskite in the temperature range 4.2 K and 450 K has been investigated using high-resolution time-of-flight neutron powder diffraction and literature values of the isobaric heat capacity. At all measured temperatures, BaZrO3 is cubic, space group $$Pm\overline{3} m$$, with no clear evidence for diffuse scattering at critical points of the primitive cubic Brillouin zone. Simultaneous fitting of the temperature dependences of the isochoric heat capacity and unit cell volume showed the thermophysical properties of BaZrO3 were consistent with a two-term Debye model in which the cations and anions behave independently of one another with Debye temperatures of 220(2) K and 730(5) K, respectively. This model is further consistent with the temperature variations of the atomic displacement parameters fitted to a modified Debye model in which the vibrational Debye temperatures of the anion are significantly larger than those associated with the cations. The evolution of the crystallographic parameters of BaZrO3 is compared to those of BaCeO3, for barium in the cavity site, and SrZrO3, for zirconium in the octahedral site.