Dipole Moment Method Research Articles

Robust retrieval method of crystal transition dipole moments by high-order harmonic spectrum

According to the three-step model for solid high-order harmonic generation, there is a one-to-one correspondence between the emitted photon energy and the band gap where the electron-hole pair is annihilated. In the tunneling excitation regime, as the electron-hole pair is mostly created in the vicinity of the minimum band gap, the conversion efficiency of the high-energy photon should be approximately proportional to the square of the transition dipole moment at the $\mathbf{k}$ point where the high-harmonic photon is emitted. Based on this picture we propose that a high-order harmonic spectrum could be a strong tool to reconstruct the shape of $\mathbf{k}$-dependent transition dipole moments with the band dispersion and the laser field known. Two real systems, e.g., MgO and ZnO, are taken as samples to verify our idea. The reconstructed shape of the transition dipole moments shows small variation as the laser parameters, such as intensity, wavelength, and pulse duration, are tuned in wide ranges, which proves this scheme is robust.

Analysis, design and testing of a rolling magnet harvester with diametrical magnetization for train vibration

Harvesting energy from ambient vibrations, particularly vibrations of a train, is very useful to build a transportation Internet of Things. This paper presents an electromagnetic vibration energy harvester (VEH) based on a cylindrical rolling magnet (RM) and one or three fixed magnets (FMs). This VEH can reach mono-stable and tri-stable potential energy states by changing the number of FMs, and enhance the nonlinearity of the system by reducing the vertical gap between the RM and FMs. Firstly, a theoretical model of the proposed VEH is established. During model construction, the commonly used dipole moment method (DMM) is found unsuitable for calculating the magnetic restoring force acting on the RM since the DMM cannot consider influences of magnet dimensions. Thus, the finite element method is applied. A position-varying factor is exploited to accomplish the electromagnetic coupling of the system. The occurrence of RM slip and the differences between its rolling and sliding effects are investigated. Then, frequency-sweeping tests are performed to understand the dynamical characteristics and energy harvesting capacity of the VEH. The experimental and simulated results under small-magnitude excitations exhibit similar trends, demonstrating the suitability of the theoretical model. The VEH with one FM achieves its maximum instantaneous power of 40.6 mW at 8.0 Hz (9.8 mW at 7.5 Hz for the VEH with three FMs). Finally, the application of this VEH for scavenging energy from the lateral vibration of a metro car body is explored in the laboratory, which suggests its high potential for powering a self-contained onboard monitoring node on a metro train.

Experimental and Theoretical Conformational Analysis of Tris(4-methylphenyl)phosphine and Its Chalcogenides

Conformational analysis of tris(4-methylphenyl)phosphine and its oxide, sulfide, and selenide has been performed by the dipole moment method and DFT quantum chemical calculations at the B3PW91/ 6-311++G(df,p) level of theory. The title compounds have been found to exist in solution as a single symmetrical conformer with gauche,gauche,gauche orientation of the substituents on the phosphorus atom with respect to the P=X bond (X = LEP, O, S, Se).

A Dipole-Moment-Based Formulation for Numerically Efficient Analysis of Scattering From Truncated Periodic Structures

Numerical analysis of truncated periodic structures by utilizing conventional method of moments (MoM) technique is challenging because the number of unknowns involved is often very large; hence, the computational cost is high. This letter presents a novel approach, based on the dipole moment (DM) method, for analyzing electromagnetic scattering from truncated periodic structures whose geometrical and/or material properties vary locally from those of a strictly doubly infinite periodic structure. The main advantage of using the DM method is that it provides convenient closed-form expressions for the scattered fields, facilitating the matrix computation in the context of the MoM much more efficiently than when the conventional Rao–Wilton–Glisson (RWG) type of basis functions are used for the same computation. Numerical results obtained by using the proposed approach are compared with those derived from a commercial MoM software package, and good agreement is found. The time advantage is clearly evident from this comparison.

Effect of shape deformation on the dielectrophoretic force on a vesicle under axisymmetric non-uniform alternating electric field

The dielectrophoresis of nearly spherical vesicles is commonly modeled using the Dipole Moment Method to estimate the dielectrophoretic force and the drag on the particle is assumed to be the same as the Stokes drag for a rigid spherical particle. We recently (Sinha and Thaokar, J Phys Cond Matt, 2018) showed that this is in agreement with analysis carried out using a more rigorous Maxwell stress method, atleast to the leading order in the shape deformation. This is essentially due to the decoupling of shape deformation and the dielectrophoretic velocity at this order of expansion. In this work, we extend the study to include the effect of shape deformation on the dielectrophoresis of a vesicle in a mixed uniform-quadrupole field. Since the deformation is frequency dependent, the correction to dielectrophoretic force is also expected to be frequency and conductivity dependent. Our analysis shows that the first order corrections are very strong and that the leading order analysis is valid only to very small shape deviations from a spherical vesicle.

Iterative Dipole Moment Method for the Dielectrophoretic Particle-Particle Interaction in a DC Electric Field

Electric force is the most popular technique for bioparticle transportation and manipulation in microfluidic systems. In this paper, the iterative dipole moment (IDM) method was used to calculate the dielectrophoretic (DEP) forces of particle-particle interactions in a two-dimensional DC electric field, and the Lagrangian method was used to solve the transportation of particles. It was found that the DEP properties and whether the connection line between initial positions of particles perpendicular or parallel to the electric field greatly affect the chain patterns. In addition, the dependence of the DEP particle interaction upon the particle diameters, initial particle positions, and the DEP properties have been studied in detail. The conclusions are advantageous in elelctrokinetic microfluidic systems where it may be desirable to control, manipulate, and assemble bioparticles.

Polarity and structure of derivatives of bis(2-phenylethyl)selenophosphinic acid

Abstract Conformational analysis of derivatives of bis(2-phenylethyl)selenophosphinic acid was carried out by the method of dipole moments and density functional theory calculations. The conformations of the examined compounds fit into the overall conformational picture for the PIV compounds: these derivatives exist as conformational equilibrium of non-eclipsed gauche and trans forms with propeller arrangement of the substituents relative to the P=Se bond. We stipulate that the eclipsed cis orientation of substituent may be caused by the formation of H-contact.

Three-Dimensional Interaction of a Large Number of Dense DEP Particles on a Plane Perpendicular to an AC Electrical Field

The interaction of dielectrophoresis (DEP) particles in an electric field has been observed in many experiments, known as the “particle chains phenomenon”. However, the study in 3D models (spherical particles) is rarely reported due to its complexity and significant computational cost. In this paper, we employed the iterative dipole moment (IDM) method to study the 3D interaction of a large number of dense DEP particles randomly distributed on a plane perpendicular to a uniform alternating current (AC) electric field in a bounded or unbounded space. The numerical results indicated that the particles cannot move out of the initial plane. The similar particles (either all positive or all negative DEP particles) always repelled each other, and did not form a chain. The dissimilar particles (a mixture of positive and negative DEP particles) always attracted each other, and formed particle chains consisting of alternately arranged positive and negative DEP particles. The particle chain patterns can be randomly multitudinous depending on the initial particle distribution, the electric properties of particles/fluid, the particle sizes and the number of particles. It is also found that the particle chain patterns can be effectively manipulated via tuning the frequency of the AC field and an almost uniform distribution of particles in a bounded plane chip can be achieved when all of the particles are similar, which may have potential applications in the particle manipulation of microfluidics.

Polarity and structure of P(X)-modified (X = O, S) arylcarbamoylmethylphosphine oxides and sulfides

As shown by the dipole moment method and quantum chemical calculations, (arylcarbamoylmethyl) diphenylphosphine oxides and sulfides exist as equilibrium mixtures of several rotational isomers stabilized by H · · · X intramolecular hydrogen bonds (X = O, S). The most energetically favorable rotamer and its fraction have been determined for each compound.

Effects of the CO₂ Guest Molecule on the sI Clathrate Hydrate Structure.

This paper analyzes the structural, energetic and mechanical properties of carbon dioxide hydrate clathrates calculated using finite cluster and periodic ab initio density-functional theory methodologies. Intermolecular interactions are described by the exchange-hole dipole moment method. The stability, gas saturation energetics, guest–host interactions, cage deformations, vibrational frequencies, and equation of state parameters for the low-pressure sI cubic phase of the CO2@H2O clathrate hydrate are presented. Our results reveal that: (i) the gas saturation process energetically favors complete filling; (ii) carbon dioxide molecules prefer to occupy the larger of the two cages in the sI structure; (iii) blue shifts occur in both the symmetric and antisymmetric stretching frequencies of CO2 upon encapsulation; and (iv) free rotation of guest molecules is restricted to a plane parallel to the hexagonal faces of the large cages. In addition, we calculate the librational frequency of the hindered rotation of the guest molecule in the plane perpendicular to the hexagonal faces. Our calculated spectroscopic data can be used as signatures for the detection of clathrate hydrates in planetary environments.

Particle interactions in three-dimensional electrical field simulated by iterative dipole moment method

The dielectrophoresis (DEP) interactions of a few particles in a uniform two-dimensional (2D) electrical field have well been studied by Maxwell stress tensor (MST) method. Multiple particle interactions in three-dimensional (3D) electrical field are investigated in this work using iterative dipole moment (IDM) method which is an analytic algorithm without complicated numerical computations to solve for electrical field. The interactive DEP forces of particles calculated by IDM are found to be well agreed with those of MST method and much simple to implement. Using IDM method, a series of examples of multiple particles interactions and particle chains in a 3D uniform DC electrical field is presented. Randomly distributed similar dense particles (either all positive DEP (pDEP) or all negative DEP (nDEP) particles) in 3D uniform electrical field can generally form chains in lines parallel to the electrical field, except the case that all similar particles are in a plane perpendicular to the electrical field where the particles repel each other and move away in the plane. Randomly distributed dissimilar dense particles (mixture of pDEP and nDEP particles) can form (1) chains in lines, (2) clusters in a plane or (3) 3D groups. The chains, clusters and groups are of staggered arrangements of pDEP and nDEP particles, which are perpendicular to the electrical field.

Iterative dipole moment method for the interaction of multiple dielectrophoretic particles in an AC electrical field

Dielectrophoresis (DEP) for bio-particle manipulation has been drawing much attention in recent years. The equivalent dipole moment method (EDM) has widely been used to calculate DEP forces on single particle, but this method falls short to describe the interaction between neighboring particles. The Maxwell stress tensor method (MST) is theoretically rigorous for particle interaction, but its complicated numerical computation makes it difficult to implement in practice. In this paper, an iterative dipole moment method (IDM) is presented to investigate the interaction of multiple dielectrophoretic particles in a two-dimensional AC electric field. Without cumbersome numerical computation, the inter-particle forces, the particle trajectories and chain patterns calculated by the IDM method are found to be well consistent with those by the MST method for some published results and experimental observations. Furthermore, it is found that the final stable particle chain patterns strongly depend on the initial configuration of the particle distribution. An arbitrary small disturbance to the particle locations may lead to dramatically different motion trajectories and final particle chains. By tuning the frequency of AC field, the particles can be transformed between positive DEP particles and negative DEP particles, which results in different particle chains as well.

Storage Ring EDM Experiments

Dedicated storage ring electric dipole moment (EDM) methods show great promise advancing the sensitivity level by a couple orders of magnitude over currently planned hadronic EDM experiments. We describe the present status and recent updates of the field.

Iterative dipole moment method for calculating dielectrophoretic forces of particle-particle electric field interactions

Dielectrophoresis (DEP) is one of the most popular techniques for bio-particle manipulation in microfluidic systems. Traditional calculation of dielectrophoretic forces of single particle based on the approximation of equivalent dipole moment (EDM) cannot be directly applied on the dense particle interactions in an electrical field. The Maxwell stress tensor (MST) method is strictly accurate in the theory for dielectrophoretic forces of particle interaction, but the cumbersome and complicated numerical computation greatly limits its practical applications. A novel iterative dipole moment (IDM) method is presented in this work for calculating the dielectrophoretic forces of particle-particle interactions. The accuracy, convergence, and simplicity of the IDM are confirmed by a series of examples of two-particle interaction in a DC/AC electrical field. The results indicate that the IDM is able to calculate the DEP particle interaction forces in good agreement with the MST method. The IDM is a purely analytical operation and does not require complicated numerical computation for solving the differential equations of an electrical field while the particle is moving.

Dipole moments and quantum chemical study of the structure of furan-containing gem-bromonitroethenes

As shown by the dipole moment method and quantum chemical calculations, 1-(furan-2-yl)-2-nitroethene and 1-nitro-2-(5-nitrofuran-2-yl)ethenes exist in solution as E-s-trans isomers while 1-bromo-2- (5-bromofuran-2-yl)-1-nitroethene and 1-bromo-1-nitro-2-(5-nitrofuran-2-yl)ethene have Z-s-cis configuration.

Phosphoryl- and thiophosphoryl-functionalized enamino ketones. Polarity and conformational analysis

The polarity and conformational behavior of some phosphorus-containing enamino ketones have been determined by the dipole moment method, IR spectroscopy, and quantum chemical calculations. 3-[2-[(Diphenylphosphoryl)methyl]phenylamino]-1-phenylprop-2-en-1-one has been found to exist as the single Z isomer. 3-[2-(Diphenylphosphoryl)phenylamino]-1-phenylprop-2-en-1-one and 3-[2-(diphenylphosphorothioyl) phenylamino]-1-phenylprop-2-en-1-one exist in equilibrium between the Z and E isomers, the latter prevailing.

A new method for the interaction between multiple DEP particles: iterative dipole moment method

Dielectrophoresis for bio-particle manipulation has been drawing much attention in recent years. The equivalent dipole moment has been widely used to calculate dielectrophoretic forces on a particle, but this method falls short to describe the interaction between neighboring particles. The Maxwell stress tensor method (MST) is theoretically rigorous for particle interaction, but it will cost huge computing resource. In this paper, an iterative dipole moment method (IDM) is presented to investigate the interaction between multiple dielectrophoretic particles in a two-dimensional electric field. Without any cumbersome numerical computation, the inter-particle forces and the particle trajectories calculated by the IDM method are found to be in good agreement with those by the MST method for some published results. Furthermore, it is found that the final stable particle chain patterns strongly depend on the initial configuration of the particle distribution. An arbitrary small disturbance to the particle locations may lead to dramatically different motion trajectories and final particle chains.

Synthesis, polarity, and structure of 2-chloro-N-[2-(methylsulfanyl)phenyl]- and 2-(diphenylthiophosphoryl)-N-[2-(methylsulfanyl)phenyl]acetamides

Conformations of 2-chloro-N-[2-(methylsulfanyl)phenyl]- and 2-(diphenylthiophosphoryl)-N-[2-(methylsulfanyl)phenyl]acetamides have been studied by the dipole moment method and quantum chemical calculations. 2-(Diphenylthiophosphoryl)-N-[2-(methylsulfanyl)phenyl]acetamide has been found to exist as an equilibrium mixture of two conformers with synclinal and anticlinal orientations of the $${C_{s{p^3}}} - {C_{s{p^2}}}$$ and P=S bonds. 2-Chloro-N-[2-(methylsulfanyl)phenyl]acetamide is represented by one preferred conformer.

Numerical study of particle chains of a large number of randomly distributed DEP particles using iterative dipole moment method

AbstractBACKGROUNDDielectrophoresis (DEP) has widely been used to manipulate bio‐particles in microfluidic system. The calculation of DEP interaction of a large number of dense particles has been a challenging issue. The Maxwell stress tensor (MST) method is strictly accurate in theory for DEP forces, but the complicated numerical computation is very difficult to implement. An iterative dipole moment method (IDM) is proposed in this paper to study the interaction forces and particle chains of a large number of dense particles in a uniform electrical field.RESULTSThe numerical example of ten particles interaction confirms that the IDM is able to calculate particle interaction forces in good agreement with the MST method. Particle chains of fifty randomly distributed dense particles in a uniform electrical field were simulated using the IDM method and were well consistent with experimental observations. Particle chains of different particle sizes are also investigated.CONCLUSIONThe interaction forces of DEP particles calculated by the IDM method are found to be in good agreement with those obtained using the Maxwell stress tensor (MST) method and easy to implement. The simulated particle chains show essential characteristics well consistent with experimental observations. © 2015 Society of Chemical Industry

Acceleration of the Impedance Matrix Filling for Marching-on-in-Degree Method by Equivalent Dipole Moment

In this article, the equivalent dipole moment method is employed to accelerate the marching-on-in-degree method for the time-domain combined field integral equation. Each element can be viewed as a dipole model when the distance between the source and the testing basis functions is beyond a threshold distance. In this way, the impedance matrix elements of each order can be easily computed by a simple procedure, and the computational time is reduced significantly for transient electromagnetic scattering. Numerical results are presented to demonstrate the efficiency of the proposed method for electromagnetic scattering from perfect electric conductor objects.