Dipole Interaction Model Research Articles

The reverse-DADI method: Computation of frequency-dependent atomic polarizabilities for carbon and hydrogen atoms in hydrocarbon structures

A specific method, combining some ingredients of the well-known DDA and PDI approaches, has been developed in our group since many years to calculate the absorption cross-sections of carbonaceous nanoparticles based on their atomistic details. This method, here named the Dynamic Atomic Dipole Interaction (DADI) model, requires the knowledge of the position and frequency-dependent polarizability of each atom constituting the nanoparticles. While the atomic positions can be quite easily obtained, for example as the results of molecular dynamics simulations, obtaining the frequency-dependent atomic polarizabilities is a trickier task. Here, a fitting procedure, named the reverse-DADI method, has been applied to calculate the frequency-dependent atomic polarizability values for carbon and hydrogen atoms involved in aromatic cycles or in aliphatic chains, on the basis of frequency-dependent molecular polarizabilities of various PAH and alkane molecules, calculated with the TD-DFT theory, in the UV–Visible range. Then, using these frequency-dependent atomic polarizabilities as input parameters in the DADI model has been shown to lead to an accurate representation of the absorption cross-sections of various PAH and alkane molecules with respect to the corresponding values obtained at the TD-DFT level, with however the great advantage of a much shorter time of calculations. Furthermore, these results are indications of a good transferability of the frequency-dependent atomic polarizability values obtained here to any C or H atom of any PAH or alkane molecule. This opens the way for building large databases of optical properties for carbonaceous species of atmospheric or astrophysical interests.

Magnetorheological response of Permalloy@ styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene elastomers as a function of filler concentration

AbstractDeveloping advanced magnetorheological elastomers (MREs) with a range of specific characteristics is essential for matching the growing demands from a wide spectrum of applications such as automotive, healthcare, sensors, and actuators. However, the compatibility problems between constituents and the low magnetorheological (MR) effect have limited their performance and integration into actual applications. Here, a novel MRE consisting of styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene (SEBS) and Ni‐rich Permalloy (Ni80Fe17Mo3) has been developed with remarkable functional properties. The correlation between the filler concentration and microstructural, mechanical, thermal, magnetic, and MR properties is reported. The incorporation of Ni‐rich Permalloy has a reinforcement effect in the polymer matrix and leads to an improvement of the thermal stability. Further, the saturation magnetization and remanence of the composites increase with increasing filler content. In particular, the saturation magnetization increases from 14.3 to 41.9 A m2/kg, and the remanence from 1.2 to 4.0 A m2/kg when the concentration increases from 20 to 60 wt%. Finally, the MR effect of composites with 20, 40, and 60 wt% filler content is 8%, 15%, and 35%, respectively. A magnetic dipole interaction model is used to discuss the MR effect and a relation between the MR effect and the main parameters affecting it is proposed. Importantly, the obtained MR values are higher when compared with related composites for the same magnetic content, and for the same or similar polymeric matrices, demonstrating the suitability of the developed materials for the fabrication of high‐response functional MR devices.

K-Ion Slides in Prussian Blue Analogues.

We study the phenomenology of cooperative off-centering of K+ ions in potassiated Prussian blue analogues (PBAs). The principal distortion mechanism by which this off-centering occurs is termed a "K-ion slide", and its origin is shown to lie in the interaction between local electrostatic dipoles that couple through a combination of electrostatics and elastic strain. Using synchrotron powder X-ray diffraction measurements, we determine the crystal structures of a range of low-vacancy K2M[Fe(CN)6] PBAs (M = Ni, Co, Fe, Mn, Cd) and establish an empirical link between composition, temperature, and slide-distortion magnitude. Our results reflect the common underlying physics responsible for K-ion slides and their evolution with temperature and composition. Monte Carlo simulations driven by a simple model of dipolar interactions and strain coupling reproduce the general features of the experimental phase behavior. We discuss the implications of our study for optimizing the performance of PBA K-ion battery cathode materials and also its relevance to distortions in other, conceptually related, hybrid perovskites.

Properties and influence of magnetic fields on iron particles of anisotropic magnetorheological elastomers

The magnetorheological elastomer (MRE) is an intelligent material whose mechanical properties can be rapidly adjusted under a magnetic flux density. This material’s mechanical properties change due to the interaction between the iron particles inside the material. Understanding the influence of magnetic flux on iron particles in MRE materials is essential. Studies have proven that the distance and angle of inclination between iron particles significantly affect the magnetic flux density and the interaction force between the particles. Therefore, the distribution of iron particles substantially affects the material’s properties. However, understanding magnetic flux through magnetic particles is necessary to improve the material’s mechanical properties and to design magnetic field systems in systems using the materials. This study maps three problems affecting magnetic flux density to the properties of MRE. First, the mechanical characteristics of the MRE were presented in the frequency, amplitude, magnetic flux density, and magnetic flux inclination domains relative to the particle chain. Next, the influence of the magnetic flux on the particle chain was investigated based on the dipole interaction model and the magnetic force on iron particles. The finite element method also explored the magnetic flux distribution in the MRE material. Finally, the response of the single-degree-of-freedom damping system is tested experimentally. The results show that the influence of the magnetic flux on the iron particles in the MRE material is significant. The research results aim to improve the mechanical properties of MRE materials.

Accurate and Interpretable Dipole Interaction Model-Based Machine Learning for Molecular Polarizability.

Polarizabilities play significant roles in describing dispersive and inductive interactions of the atom and molecular systems. However, an accurate prediction of molecular polarizabilities from first principles is computationally prohibitive. Although physical models or statistical machine learning models have been proposed, either a lack of accurate description of local chemical environments or demanding a large number of samples for training has limited their practical applications. In this study, we combine a physically inspired dipole interaction model and an accurate neural network method for predicting the polarizability tensors of molecules. With the local chemical environment precisely described and the requirement of rotational covariance naturally fulfilled, this hybrid model is proven to give an accurate molecular polarizability prediction, essentially reducing the number of training samples. The atomic polarizabilities are physically interpretable and transferable to larger molecules unseen in the training set. This promising method may find its wide range of applications, such as spectroscopic simulations and the construction of polarizable force fields.

Dipole–dipole interactions for inhibiting solvent co-intercalation into a graphite anode to extend the horizon of electrolyte design

A dipole–dipole interaction model, in which the non-solvents weaken Li+-solvents’ strength, facilitating desolvation and thus ameliorating graphite compatibility, is developed to expedite electrolyte innovation in LIBs.

A CRYSTAL-based parameterization of carbon atom dynamic polarizabilities to compute optical properties of curved carbonaceous nanostructures

The radiative forcing of dust particles in Earth atmosphere is still poorly characterized. A better estimation of the absorption cross section of dust particles in the UV-visible part of the spectrum is thus needed. Among the methods used for this purpose, the Atomic Point Dipole Interaction model has the distinctive advantage of being sensitive to the atomistic geometry of the particle and to the chemical functions it contains. However, this requires an adequate parameterization of the atomic polarizabilities for all the atomic species forming the particle, over the UV-visible spectrum. In this paper, we illustrate how new methodological improvements based on quantum chemistry, allow taking into account the curvature of the carbon network in the parametrization of the carbon atomic polarizabilities, using the C $$_{60}$$ molecule to fit the adequate set of parameters. We thus show how this leads to significant differences in the computed curves of the absorption cross section of pure carbonaceous nanoparticles as a function of the frequency, with respect to calculations performed using parameters issued from graphite.

An Application of Dipole–Dipole Interaction Model in Stacking Dimers Including Protonated Arginine Residue

An Application of Dipole–Dipole Interaction Model in Stacking Dimers Including Protonated Arginine Residue

Enhanced asymmetric giant magneto-impedance effect and linearity in sandwich FePd/FINEMET/FePd composite ribbons

The FePd/FINEMET/FePd composite ribbons with sandwich structure were designed by magnetron sputtering. The morphology, magnetic properties and asymmetric giant magneto-impedance (AGMI) effect of FePd/FINEMET/FePd composite ribbons show that the sandwich structure can significantly improve the GMI effect of FINEMET ribbon with a homogeneous structure. Results have demonstrated that the magnetic dipole interaction between the FePd layer and the FINEMET ribbon makes the FePd/FINEMET/FePd composite ribbons obtain a larger GMI effect at low frequencies. The maximum GMI ratio of FePd/FINEMET/FePd composite ribbons reaches 51 %, which is 2.2 times that of bare FINEMET ribbon. The asymmetry degree of GMI curves is up to 85 %. It has the ability to significantly enhance the GMI effect, linearity and reduced the characteristic frequency of composite materials. The experimental results can be explained by the magnetic dipole interaction model. It is a profound significance in the development of a magnetic sensor that can increase the GMI ratio and the linearity.

Accurate Atom-Dipole Interaction Model for Prediction of Electro-optical Properties: From van der Waals Aggregates to Covalently Bonded Clusters.

This work aims at the accurate estimation of the electro-optical properties of atoms and functional groups in organic crystals. A better understanding of the nature of building blocks and the way they interact with each other enables more efficient prediction of self-assembly, and thus physical properties in condensed matter. We propose a modified version of an atom-dipole interaction model that is based on atomic dipole moments calculated from the quantum theory of atoms in molecules. The method is very reliable for the prediction of various optical and electric properties in diverse chemical environments, ranging from hydrocarbon molecules bonded by dispersive interactions to polar rings connected by hydrogen bonds, or even polymeric structures whose monomers are covalently linked. Distributed polarizabilities and electrostatic potentials are compared to those obtained using a complete quantum-mechanical approach on finite-size aggregates. Our electrostatic approximation recovers isotropic polarizabilities with an accuracy of ca. 5 au and electrostatic potentials of ca. 0.05 au, even in the worst-case scenario in which polarization and charge-transfer effects are large. Functional groups are highly exportable, estimating the properties of small peptides and polyaromatics with a maximum deviation as low as ca. 15%.

Shear response of magnetorheological fluid with Zn0.2Fe2.8O4 sub-micron hollow spheres

Magnetorheological (MR) fluids with Fe3O4 particles are widely studied nowadays due to their soft magnetic nature, controllable morphology, and better chemical stability as compared to their metallic counterpart. However, they can be even more advantageous under Zn doping with elevated magnetization and hollow configuration with low density, making them more active, stable, and dispersible in the carrier fluid. Here, we report the preparation of MR fluids with Zn0.2Fe2.8O4 sub-micrometer hollow spheres and their steady-state MR response under the application of a magnetic field. The MR fluid follows the Bingham plastic nature with a yielding behavior. The variation of yield stress with the applied magnetic field is explained in the context of a newly developed dipolar interaction model.

Quantum delocalization, gauge, and quantum optics: Light-matter interaction in relativistic quantum information

We revisit the interaction of a first-quantized atomic system (consisting of two charged quantum particles) with the quantum electromagnetic field, pointing out the subtleties related to the gauge nature of electromagnetism and the effect of multipole approximations. We connect the full minimal-coupling model with the typical effective models used in quantum optics and relativistic quantum information such as the Unruh-DeWitt (UDW) model and the dipole coupling approximation. We point out in what regimes different degrees of approximation are reasonable and in what cases effective models need to be refined to capture the features of the light-matter interaction. This is particularly important when considering the center of mass (COM) of the atom as a quantum system that can be delocalized over multiple trajectories. For example, we show that the simplest UDW approximation with a quantum COM fails to capture crucial R\"ontgen terms coupling COM and internal atomic degrees of freedom with each other and the field. Finally we show how effective dipole interaction models can be covariantly prescribed for relativistically moving atoms.

Correction to “Solid Oganesson via a Many-Body Interaction Expansion Based on Relativistic Coupled-Cluster Theory and from Plane-Wave Relativistic Density Functional Theory”

Many-body potentials up to fourth order are constructed using nonrelativistic, scalar-relativistic, and relativistic coupled-cluster theory to accurately describe the interaction between superheavy oganesson atoms. The obtained distance-dependent energy values were fitted to extended two-body Lennard-Jones and three-body Axilrod-Teller-Muto potentials, with the fourth-order term treated through a classical long-range Drude dipole interaction model. From these interaction potentials, spectroscopic constants for the oganesson dimer and solid-state properties were obtained. Furthermore, these high-level results are compared to scalar-relativistic and two-component plane-wave DFT calculations based on a tailor-made projector augmented wave pseudopotential (PAW-PP) and newly derived parameters for Grimme's dispersion correction. It is shown that the functionals PBE-D3(BJ), PBEsol, and in particular SCAN provide excellent agreement with the many-body reference for solid oganesson. Finally, the results for oganesson are compared and related to the lighter rare gas elements, and periodic trends are discussed.

A solvable problem in statistical mechanics: The dipole-type Hamiltonian mean field model

The present study documents a type of mean field approximation inspired by the dipole interaction model, which is analytically solved in the canonical and microcanonical ensembles. The current calculations were derived from the Hamiltonian mean field model developments. After describing the canonical partition function, the free and internal energies, magnetization, and specific heat are derived and graphically depicted. In the microcanonical ensemble, the entropy is calculated as well as other thermodynamic properties. The system shows a second-order phase transition emphasizing that both methods coincide, which is only valid only in equilibrium. In addition, the current model represents a nonsymmetric Hamiltonian mean field model that shows a phase transition.

Bond-Dependent Thole Model for Polarizability and Spectroscopy.

We present a new model for the calculation of molecular polarizabilities from effective atomic polarizabilities. This model is based on the Thole modified dipole interaction model for molecular polarizabilities, where the total polarizability is computed as a sum of effective atomic polarizabilities modified by dipole-dipole interactions. We extend this model by making the atomic polarizabilities explicit functions of the interatomic distances, scaling them by the radius of the volume an atom occupies in a molecule. We use the SCAN functional to show that this model, denoted TholeL, yields accurate molecular polarizabilities with little dependence on the training set. We also demonstrate that the TholeL model yields accurate polarizabilities for configurations far from the ground state structure for a wide range of molecules. Finally, we show that the TholeL model can be used to generate accurate Raman spectra for water, crystalline urea, and urea in water from ab initio molecular dynamics simulations.

Solid Oganesson via a Many-Body Interaction Expansion Based on Relativistic Coupled-Cluster Theory and from Plane-Wave Relativistic Density Functional Theory.

Many-body potentials up to fourth order are constructed using nonrelativistic, scalar-relativistic, and relativistic coupled-cluster theory to accurately describe the interaction between superheavy oganesson atoms. The obtained distance-dependent energy values were fitted to extended two-body Lennard-Jones and three-body Axilrod-Teller-Muto potentials, with the fourth-order term treated through a classical long-range Drude dipole interaction model. From these interaction potentials, spectroscopic constants for the oganesson dimer and solid-state properties were obtained. Furthermore, these high-level results are compared to scalar-relativistic and two-component plane-wave DFT calculations based on a tailor-made projector augmented wave pseudopotential (PAW-PP) and newly derived parameters for Grimme's dispersion correction. It is shown that the functionals PBE-D3(BJ), PBEsol, and in particular SCAN provide excellent agreement with the many-body reference for solid oganesson. Finally, the results for oganesson are compared and related to the lighter rare gas elements, and periodic trends are discussed.

A new three-dimensional magneto-viscoelastic model for isotropic magnetorheological elastomers

In this work, a four-parameter fractional derivative viscoelastic model was developed to describe the dynamic shear behaviour of magnetorheological elastomers (MREs) as a function of the matrix, particle content and magnetic field. The material parameters were obtained from experimental data measured with a Physica MCR 501 rheometer from the Anton Paar Company, equipped with a magnetorheological cell. The synthetised isotropic MRE samples were based on room-temperature vulcanising silicone rubber and spherical carbonyl iron powder micro particles as fillers, and seven volumetric particle contents were studied. The influence of particle contents was included in each parameter of the four-parameter fractional derivative model. The dependency of the storage modulus as a function of an external magnetic field (magnetorheological (MR) effect) was studied, and a dipole–dipole interaction model was used. A new three-dimensional magneto-viscoelastic model was developed to couple the viscoelastic model, the particle-matrix interaction and the magneto-induced modulus model, which predicts the influence of the magnetic field and the particle content in the MR effect of isotropic MREs.

Effect of long- and short-range interactions on the thermodynamics of dipolar spin ice

The thermodynamic properties of dipolar spin ice on square, honeycomb and shakti lattices in the long-range and short-range dipole interaction models are studied. Exact solutions for the density of states, temperature dependencies of heat capacity, and entropy are obtained for these lattices with a finite number of point dipoles by means of complete enumeration. The magnetic susceptibility and average size of the largest low-energy cluster are calculated for square spin ice by means of Wang–Landau and Metropolis methods. We show that the long-range interaction leads to a blurring of the energy spectrum for all considered lattices. The inclusion of the long-range interaction leads to a significant change in the thermodynamic behaviour. An additional peak of heat capacity appears in the case of the honeycomb lattice. The critical temperature shifts in the direction of low or high temperatures; the direction depends on the lattice geometry. The critical temperature of the phase transition of square spin ice in the long-range model with frustrated ground states is obtained with the Wang–Landau and Metropolis methods independently.

Nanoscale Patterns on Polar Oxide Surfaces

Polar ionic surfaces with bulk termination are inherently unstable because of their diverging electrostatic surface energy. Nevertheless, they are frequently observed in nature, mainly because of charge neutralization by adsorbates, but occur also under atomically clean conditions. Several mechanisms have been invoked to explain the stability of atomically clean polar surfaces, but the frequently observed periodic nanoscale pattern formation has not yet been explained. Here we propose that long-range interactions between alternating electropositive and electronegative regions of different surface terminations minimize the electrostatic energy of the surface and thus stabilize the nanoscale pattern. This is illustrated using the example of polar Fe oxide surfaces by combining scanning tunneling microscopy and spectroscopy results with results from density functional theory-based calculations and dipole–dipole interaction models.

Orientation-Sensitive Peptide-Induced Plasmonic Circular Dichroism in Silver Nanocubes

Polyproline II-based helical peptides were adsorbed to silver nanocubes through a cysteine linker and induced circular dichroism (CD) in two of their plasmon resonance modes. Inversion of the peptide’s orientation with respect to the surface led to inversion of the plasmonic CD signal. This phenomenon could not be explained by the simple molecule–plasmon dipolar interaction model and could be due to the multipolar nature of the plasmon modes. Elongation of the polyproline peptide led to a significant increase of the induced CD signal. Surprisingly, the effect did not change with sharpening of the edges of the silver nanocubes. The change to a polyproline I helix caused nulling of the induced plasmonic CD.