Total Polarizability Research Articles

Molecular Simulation Analysis of Polyurethane Molecular Structure under External Electric Field.

Polyurethane (PU) materials are extensively utilized in power equipment. This paper introduces a comprehensive evaluation method that combines electromagnetics and computational chemistry based on the Density Functional Theory (DFT) to elucidate the impact of external electric fields on the molecular structure of PU during electrical contact. The study focuses on the microstructural and molecular energy changes in the hard (HS) and soft (SS) segments of PU under the influence of an electric field of uniform intensity. Findings indicate that the total energy of HS molecules decreases markedly as the electric field intensity increases, accompanied by a significant rise in both the dipole moment and polarizability. Conversely, the total energy and polarizability of the SS molecules decrease, while the dipole moment experiences a slight increase. Under the influence of a strong electric field, HS molecules tend to stretch towards the extremities of the main chain, leading to structural instability and the cleavage of hydroxyl O-H bonds. Meanwhile, the carbon chain of the SS molecules twists towards the center under the electric field, with no chemical bond rupture observed. At an electric field intensity of 8.227 V/nm, the HOMO-LUMO gap of the HS molecule narrows sharply, signifying a rapid decline in the molecular structure stability, corroborated by infrared spectroscopy analysis. These findings offer theoretical insights and guidance for the modification of PU materials in power equipment applications.

Evaluating the drug delivery potential of graphene, BC3, and NC3 nanosheets for cyclophosphamide: A computational study analyzing static electric field and solvent effects through DFT, TD-DFT, and NLO techniques

This study explores the interaction between cyclophosphamide (CP) and graphene (G), BC3 nanosheets (B), and NC3 nanosheets (N) under static electric fields (SEFz + 0.01 to SEFz + 0.04 a.u) using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). Negative adsorption energy (Eads) and enthalpy (ΔH) values indicate favorable complex formation in gas and water environments for CP-drug&G, CP-drug&BC3, and CP-drug&NC3. Highlighted Eads values in models B1 (−29.61 kcal/mol) and B3 (−27.18 kcal/mol) suggest strong CP-drug and BC3 nanosheet interaction. AIM, RDG, and ELF analyses confirm noncovalent interactions. Increased total polarizability (αtot) and first hyperpolarizability (βtot) indicate potential traceability of CP-drug&nanosheet complexes. SEF fields enhance dipole moment and reactivity, highlighting BC3 nanosheets as promising candidates for designing carriers and sensors for targeted CP-drug delivery. The future outline includes further investigations into the dynamics of CP-drug&nanosheet complexes and their applications in drug delivery and sensing technologies.

Synthesis, characterization and DFT studies of fluorinated aryl derivatives: Electronic and optical responses

The current study was designed to synthesize biaryls compounds viz; 2-(3,4-difluorophenyl) benzothiophene (DFPBT), 3-(3,4-difluorophenyl) quinoline (DFPQ) and 1-(3,4-difluorophenyl) naphthalene (DFPN) by means of Suzuki-Miyaura Pd(0)-catalyzed protocol. Different characterization techniques were used to evaluate the structure of desired synthesized compounds viz; H1NMR, C13NMR, FT-IR and UV–Vis analyses. Besides, DFT computations were carried out at B3LYP/6–311++ G(d, p) functional to gain an insight of key electronic properties of the synthesized compounds. The natural bonding orbital (NBO) analysis showed that molecules of these compounds should interact quite noticeably with each other in the solid phase and with polar solvent molecules. The FMO findings revealed that the ∆E value are in order; DFPN > DFPQ > DFPBT. Accordingly, DFPBT exhibited better NLO properties and possessed a slightly strong electron transfer potential than DFPQ and DFPN. A good harmony between experimental (296.4, 304.7 and 298.4 nm) and simulated (306, 305 and 298 nm) UV–Vis values was investigated in studied compounds. Furthermore, multiple functional (M062X, CAM-B3LYP, HF, M06, B3LPY, and LCBLYP) with 6–311++G(d, p) basis set were used to investigate the total dipole moment, hyperpolarizability βtot and average polarizability ⟨α⟩ values. The average polarizability ⟨α⟩ values of DFPBT, DFPQ and DFPN were 5.7, 5.7 and 5.5 times greater than urea i.e., ⟨α⟩=34.055 a.u, while, the βtot values were 5.8, 7.8 and 6.1 times more than the total values of urea. i.e., 90.527 a. u, respectively. These efficient behavior of NLO in synthesized compounds indicated the significant use of these compounds in optoelectronic devices.

The Role of Base in Reaction Performance of Photochemical Synthesis of Thiazoles: An Integrated Theoretical and Experimental Study.

Artificial intelligence (AI)/machine learning (ML) is emerging as pivotal in synthetic chemistry, offering revolutionary potential in retrosynthetic analysis, reaction conditions and reaction prediction. We have combined chemical descriptors, primarily based on Density Functional Theory (DFT) calculations, with various AI/ML tools such as Multi-Layer Perceptron (MLP) and Random Forest (RF), to predict the synthesis of 2-arylbenzothiazole in photoredox reactions. Significantly, our models underscore the critical role of the molecular structure and physicochemical characteristics of the base, especially the total atomic polarizabilities, in the rate-determining steps involving cyclohexyl and phenethyl moieties of the substrate. Moreover, we validated our findings in articles through experimental studies. It showcases the power of AI/ML and quantum chemistry in shaping the future of organic chemistry.

Fragment-Based Deep Learning for Simultaneous Prediction of Polarizabilities and NMR Shieldings of Macromolecules and Their Aggregates.

Simultaneous prediction of the molecular response properties, such as polarizability and the NMR shielding constant, at a low computational cost is an unresolved issue. We propose to combine a linear-scaling generalized energy-based fragmentation (GEBF) method and deep learning (DL) with both molecular and atomic information-theoretic approach (ITA) quantities as effective descriptors. In GEBF, the total molecular polarizability can be assembled as a linear combination of the corresponding quantities calculated from a set of small embedded subsystems in GEBF. In the new GEBF-DL(ITA) protocol, one can predict subsystem polarizabilities based on the corresponding molecular wave function (thus electron density and ITA quantities) and DL model rather than calculate them from the computationally intensive coupled-perturbed Hartree-Fock or Kohn-Sham equations and finally obtain the total molecular polarizability via a linear combination equation. As a proof-of-concept application, we predict the molecular polarizabilities of large proteins and protein aggregates. GEBF-DL(ITA) is shown to be as accurate enough as GEBF, with mean absolute percentage error <1%. For the largest protein aggregate (>4000 atoms), GEBF-DL(ITA) gains a speedup ratio of 3 compared with GEBF. It is anticipated that when more advanced electronic structure methods are used, this advantage will be more appealing. Moreover, one can also predict the NMR chemical shieldings of proteins with reasonably good accuracy. Overall, the cost-efficient GEBF-DL(ITA) protocol should be a robust theoretical tool for simultaneously predicting polarizabilities and NMR shieldings of large systems.

A controllable interlayer shielding effect in twisted multilayer graphene quantum dots.

When multilayer graphene (MLG) is subjected to a vertical electric field, electrons traverse across the layers and its interlayer electrical conductance and shielding effect exhibit remarkable diversity, leading to exotic phenomena and diverse applications in photoelectric devices. The rearrangement of electrons induced by this external field is aptly described by polarizability, which quantifies the electronic response to the applied field. In this work, we have developed a polarizability decomposition scheme based on field-induced electron density variations computed using a first-principles approach. This scheme allows us to isolate the inter- and intra-layer contributions from the total polarizability of twisted multilayer graphene (TMG) quantum dots. The inter- and intra-layer counterparts reflect the charge transfer (CT) and field shielding effects among the layers, respectively. While the strongest shield effect is observed between the outermost two layers, the largest CT change is noted in the outermost layers, but small or nearly zero CT changes in the inner layers. Significant CT and shielding effects are observed not only in strongly coupled Bernal stacking, but also in the structures misaligned from full-(AA)N stacking by a small and size-dependent twist angle. The dielectric behaviors of the TMG quantum dots of a few layers are layer-dependent and different from those of typical dielectrics. Moreover, both the shielding and CT effects exhibit variation with thickness, twist angle and disc size, suggesting controllable conductive/dielectric conversion in the vertical direction. Considering the inter- and intralayer polarizability, our study addresses the precise modulation of interlayer conductance and shielding effect for TMG quantum dots, essential for microstructure design and performance manipulation of MLG-based photoelectric devices.

Accurate and Efficient Prediction of Post-Hartree-Fock Polarizabilities of Condensed-Phase Systems.

To accurately and efficiently predict the molecular response properties (such as polarizability) at post-Hartree-Fock levels for condensed-phase systems under periodic boundary conditions (PBC) is still an unaccomplished and ongoing task. We demonstrate that static isotropic polarizabilities can be cost-effectively predicted at post-Hartree-Fock levels by combining the linear-scaling generalized energy-based fragmentation (GEBF) and information-theoretic approach (ITA) quantities. In PBC-GEBF, the total molecular polarizability of an extended system is obtained as a linear combination of the corresponding quantities of a series of small embedded subsystems of several monomers. Here, we show that in the PBC-GEBF-ITA framework, one can obtain the molecular polarizabilities and establish linear relations to ITA quantities. Once these relations are established for smaller subsystems, one can predict the polarizabilities of larger subsystems directly from the molecular wavefunction (or electron density) via ITA quantities. Alternatively, one can determine the total molecular polarizability via a linear combination equation in PBC-GEBF. We have corroborated that this newly proposed PBC-GEBF-ITA protocol is much more efficient than the original PBC-GEBF approach but is not much less accurate and that this conclusion holds for both many-body perturbation theory and the coupled cluster calculations. Good efficiency and transferability of the PBC-GEBF-ITA protocol are demonstrated for periodic systems with several hundred atoms in a unit cell.

Gladstone-Dale compatibility, electronic polarizability and vibrational spectroscopy of minerals and inorganic compounds with V4+O and V4+O2 vanadyl groups.

VO and VO2 vanadyl groups with short (typically 1.57-1.68 Å), essentially covalent, V-O bonds are common for V4+-bearing oxysalts with [5]- and [6]-coordinated vanadium. There is a clear negative correlation between vanadyl bond lengths and wavenumbers of the bands of V-O stretching vibrations in infrared spectra (in the range 1000-880 cm-1). Optical, structural and chemical data for vanadyl minerals are used to calculate Gladstone-Dale compatibility coefficients. Gladstone-Dale compatibility indices of minerals containing vanadyl bonds are compared with total electronic polarizabilities of V4+. Unlike compounds of [5]-coordinated Ti4+, for most minerals with V4+=O (vanadyl) bonds there is good agreement between measured refractive indices and those calculated based on the polarizability concept.

Structural, raman, optical and electrical studies of pure and compound crystal of magnesium sulphateheptahydrate and threonine

Pure and compound crystal of magnesium sulphate heptahydrate(MSH) and threonine (THR) is grown from aqueous solution by slow evaporation method at room temperature. The reaction between MSH and THR is confirmed by TLC test. Good quality and transparent crystals are harvested. Pure MSH and THR crystallize in orthorhombic crystal system, while compound crystal shows the presence of both the phases of MSH and THR.The crystallite size is found using the various methods are employed to estimate the crystallite sizes and the lattice strain. The Raman spectra show the presence of characteristic normal modes of vibrations of pure MSH and THR in the compound crystal.The optical band gap is estimated by using K-M function. The various optical parameters such as extinction coefficient, refractive index, optical conductivity and skin depth have been calculated and analyzed with incident photon energy. The dielectric constant and loss of all the grown crystals have exhibited normal behavior over the frequency range considered. The total polarizability of the crystals is calculated by two theoretically methods and matches well with experimental results. The complex impedance and modulus spectroscopy studies suggested the presence of grain effect in all the samples and the same is successfully modelled using R-CPE parallel circuit. Non-debye type relaxation is confirmed from β-parameter. From the Jonscher’s plot, the ideal long range pathways and diffusion limited hopping mechanism is confirmed for all the samples. The results of pure crystal of MSH and THR are compared with the compound crystal and discussed accordingly in detail.

Structural elucidation, solvent (polar and non-polar) effect on electronic characterization, non-covalent charge interaction nature, topology and pharmacological studies on NLO active l-argininium methanesufonate

Reaction of l-arginine (l-Arg) with methanesulfonic acid (l-ArgH) (CH3SO3) in aqueous solution was investigated. The method of synthesis of (l-ArgH)(CH3SO3) was solvothermal. The precursors l-arginine and methanesulfonic acid was dissolved in aqueous solution. The solution was allowed to slowly evaporate, leading to the formation of non-centrosymmetric crystals of (l-ArgH)(CH3SO3). The crystal structure was determined using X-ray diffraction analysis. Using Hirshfeld surfaces and 2D-fingerprint plots, the interactions between the crystal structures were studied. The structure is optimized using density functional theory (DFT) at the B3LYP/ 6–31 + G* level in gas phase which in turn compared with the empirically determined molecular structure in the solid state. Vibrational spectrum analyses were also used to characterise the (l-ArgH)(CH3SO3) salt. To ascertain the energy gap, the HOMO-LUMO behaviour in several solvents (polar and non-polar) has been performed. The HOMO-LUMO energies from various liquids (polar and non-polar) indicate that the molecules are interacting via charge transfer. The interaction of the lone pair, bonding, and anti-bonding molecular orbitals has been evaluated by NBO. Topology investigations also shed light on the molecule's molecular structure and reactivity. The molecular electrostatic potential illustrates the potential for electrophilic and nucleophilic sites in a molecule for different solvents. A few polar and non-polar solvents were computed for NLO characteristics such the dipole moment, total polarizability, and first order hyper polarizability in addition to the gas phase. The SHG efficiency of (l-ArgH)(CH3SO3) salt relative to KDP was found to be 0.9. SwissADME is performed to get the drug likeness of the grown (l-ArgH)(CH3SO3).

Machine Learning Prediction of Hydration Free Energy with Physically Inspired Descriptors

We present machine learning models for predicting experimental hydration free energies of molecules without any atom-, bond-, or geometry-specific input feature. Four types of physically inspired descriptors are adopted for predictions. The first type is composed of the total dipole moment, anisotropic polarizability, and vibrational analysis results of the solute molecule. The second and third types are derived from the electrostatic potential distribution of the solute. The last type includes the solvent accessible surface area and shape similarities. Several machine learning regression models are built on the basis of the FreeSolv database with ∼600 samples, showing a better performance in comparison with that of most traditional approaches and other prediction methods based on molecular fingerprints. In particular, the present descriptors are capable of predicting hydration free energies of new compounds with elements or fragments that are never seen in the training set. The importance of these descriptors, the impact of dissociation energies of specific covalent bonds, and the outliers with relatively large prediction errors are also discussed.

Substrated inhomogeneous metasurfaces analysis using interaction constant method

Inhomogeneous metasurfaces as a periodic array of supercells in which each supercell consists of different types of particles are good candidates for increasing the bandwidth in many applications. However, the presence of a substrate is often apparent in many cases; therefore, analyzing substrated inhomogeneous metasurfaces is highly attractive and important. In this paper, an efficient analysis of the plane-wave scattering by inhomogeneous substrated metasurfaces is presented using interaction constant method (ICM). In our proposed method, we calculate the total effective polarizability tensors of inhomogeneous substrated metasurfaces using both the individual polarizabilities of each particle and the closed-form interaction coefficients that relate to the interactions of the particles with each other. Since the interaction constants are calculated analytically, this method is time effective for different arrangements of particles in supercells, and with different array periods. The reflectance and transmittance of different inhomogeneous metasurfaces have been obtained and compared to full-wave simulations by a commercial EM solver, here, and this has confirmed the accuracy of the numerical results of our proposed method. Moreover, in our last example, we present a wideband terahertz absorber, and analyze its structure with our method. It seems that our proposed method is a step forward in the analysis and design of inhomogeneous substrated metasurfaces, for various applications.

Structure and microwave dielectric properties of Bi- and Ge-doped calcium molybdate

The powders of Ca1–2xBi2xMo1–xGexO4 solid solutions weresynthesized by the conventional solid state method and investigated by X–ray powder diffraction and Raman spectroscopy. The Ca1–2xBi2xMo1–xGexO4 compositions crystallize in scheelite structure (sp. gr. I41/a) at 0 x 0.4, but traces of bismuth germanates are detected by scanning electron microscopy. The x = 0.5 composition contains several phases with BiVO4- type structures. Raman spectroscopy detected the deformation of [BO4]2– polyhedra and changes in B–O bond length (B = Mo, Ge). The energy gaps were calculated from the diffuse scattering spectra by the Kubelka-Munk method. Energy gap (Eg) values decrease with x from 3.29 eV to 2.91 eV, probably due to 6s2 electrons of bismuth in the valence band and changes of the conductivity band by electrons of germanium. Such values of Eg can provide photocatalytical activity of powders under UV and visible light. The electrodynamic parameters of the ceramic sample of Ca1–2xBi2xMo1–xGexO4 were measured by the transmission line method. The average permittivity increases with x from ~10 to ~18 which correlates with theoretical ε, Vmol and total polarizability of samples. An increase in the concentration of bismuth and germanium leads to the additional resonant peaks in the spectra of ε, S11 and S21. These resonant peaks can be probably caused by the appearance of irregular structural domains of Bi atoms or induced by the increased size of grains in the ceramic samples.

Density Functional Theoretical Computational Studies on 3-Methyl 2-Vinyl Pyridinium Phosphate

The molecular structure of 3-methyl 2-vinyl pyridinium phosphate (3M2VPP) has been optimized by using Density Functional Theory using B3LYP hybrid functional with 6-311++G (d, p) basis set in order to find the whole characteristics of the molecular complex. The theoretical structural parameters such as bond length, bond angle, and dihedral angle are determined by DFT methods and are well agreed with the single crystal X-ray diffraction parameters. Theoretical vibrational, highest occupied molecular orbital - lowest unoccupied molecular orbital (HOMO-LUMO), natural bonding orbital (NBO), and electrostatic potential (ESP) analyses have also been performed. Based on the potential energy distribution (PED), the complete vibrational assignments, analysis, and correlation of the compound’s fundamental modes have been determined. Natural bonding orbital (NBO) analysis is used to evaluate the intramolecular charge transfer and hyper-conjugative interaction of the molecule. B3LYP/6-311++G (d, p) basis set determines the electronic properties such as HOMO–LUMO energies and is used to understand the kinetic stability and chemical reactivity of the studied compound. Molecular electrostatic potential (MEP) is used to investigate the electron density distribution and chemical reactive sites of 3M2VPP. The dipole moment, total polarizability, and the first-order hyperpolarizability calculations have been carried out for the studied molecule. Hirshfeld surface analysis has been done to study the intermolecular interactions in the studied complex.

Intensive linear and nonlinear optical studies of thermally evaporated amorphous thin Cu-Ge-Se-Te films

This article is devoted to completing the study of linear and nonlinear optical characteristics of thermally evaporated a-CuxGe20-xSe40Te40, CGST, (0 ≤ x ≤ 20 at.%) thin films. The film thickness and rate of deposition were fixed in 2000 Å and 100 Å/s, respectively. Optical constants of CGST-films have been deduced from spectrophotometric measurements in the spectral range 300nm-2500 nm. The VB and CB potentials have been determined; their values increase from 0.344 eV to 0.404 eV for the CB, while increases from (-0.864 eV) to (-0.641 eV) for VB, as Cu-percentage increases. Wemple-DiDomenico single oscillator model is applied to obtain dispersion energies and parameters. The single oscillator energy decreases from 2.411 eV to 2.232 eV, while the dispersion energy increases from 14.974 eV to 20.763 eV, as Cu-ration increases. Many other important optoelectrical and dielectric parameters have also been discussed, like static refractive index, average oscillator wavelength, oscillator-length strength parameters. The surface and volume energy loss functions, optical complex conductivity (real and imaginary parts), electronic polarizability, and some nonlinear optical parameters are also well-discussed. Total electronic polarizability values increase from 4.560 Å to 3.088 Å, while the plasma frequency increases from 4.200×1014 Hz to 3.970×1014 Hz. All mapped parameters have been discussed and linked to each other, as well as studying their dependence on Cu-ratio.

Measurement of the Rb87 D -line vector tune-out wavelength

We report a precision measurement of a tune-out wavelength for 87Rb using circularly polarized light. A tune-out wavelength characterizes a zero in the electric polarizability of the atom. For circularly polarized light, the total polarizability depends on both the scalar and vector polarizability components. This shifts the location of the tune-out wavelength and makes it sensitive to different combinations of atomic dipole matrix elements than the scalar polarizability alone. Using $\sigma_-$ polarized light with an an estimated purity of 0.9931(1), we observe a tune-out wavelength of 785.1522(3) nm, which agrees with theoretical expectations when small contributions from the core electrons and off-resonant valence states are taken into account.

A Novel Method for Analyzing Inhomogeneous Metasurfaces

A new method for analyzing multispectral inhomogeneous metasurfaces is presented, which includes several types of particles. Our proposed method (PM) suggests a new semianalytical technique to solve the total effective polarizabilities of inhomogeneous arrays. Here, we propose the inhomogeneity in which metasurface can be regarded as constituting arrays of periodic supercells. Closed-form relations are suggested to calculate the interaction constants inside the supercells, and the local effective polarizabilities are obtained with the aid of these relations. Then, the conventional interaction constants are used to calculate the total effective polarizabilities of an array. To evaluate the generality and accuracy of our PM, the reflection and transmission coefficients of different arrays consisting of isotropic and bianisotropic particles are analyzed with this method, and the results are compared to those of an HFSS simulator. Our method is a step forward in analyzing and synthesizing inhomogeneous and multispectral metasurfaces.

Fragment-Based Excited-State Calculations Using the GW Approximation and the Bethe-Salpeter Equation.

Herein, we present a fragment-based approach for calculating the charged and neutral excited states in molecular systems, based on the many-body Green's function method within the GW approximation and the Bethe-Salpeter equation (BSE). The implementation relies on the many-body expansion of the total irreducible polarizability on the basis of fragment molecular orbitals. The GW quasi-particle energies in complex molecular environments are obtained by the GW calculation for the target fragment plus induced polarization contributions of the surrounding fragments at the static Coulomb-hole plus screened exchange level. In addition, we develop a large-scale GW/BSE method for calculating the delocalized excited states of molecular aggregates, based on the fragment molecular orbital method and the exciton model. The accuracy of fragment-based GW and GW/BSE methods was evaluated on molecular clusters and molecular crystals. We found that the accuracy of the total irreducible polarizability can be improved systematically by including two-body correction terms, and the fragment-based calculations can reasonably reproduce the results of the corresponding unfragmented calculations with a relative error of less than 100 meV. The proposed approach enables efficient excited-state calculations for large molecular systems with reasonable accuracy.

Interlayer polarizability in twisted bilayer graphene quantum dots

Many of the intriguing properties of bilayer graphene (BLG) are related to interlayer electronic coupling. Since this coupling is sensitive to an applied electric field perpendicular to the layers, we develop a strategy for determining interlayer coupling by decomposing the total electric dipole polarizability, which measures the response of electrons to applied fields, into site-specific contributions and consequently the intralayer and interlayer components. The interlayer polarizability is evaluated from field-induced electron density variations computed with a first-principles approach for twisted BLG quantum dots (QDs). Changes in interlayer polarizability dominate the polarizability variation with twist angle. In addition to the well-recognized strong coupling in the Bernal stackings, enhanced coupling is revealed for the structures at small and size-dependent twist angles when AB stacking first appears in the outermost shell of the QD. The values of these magic angles depend on the QD size. This paper not only provides an approach for measuring interlayer coupling strength but also indicates the existence of strong interlayer coupling even at small twist angles, which could be important for understanding the properties of twisted BLG.

Full Assignment of Ab-Initio Raman Spectra at Finite Temperatures Using Wannier Polarizabilities: Application to Cyclohexane Molecule in Gas Phase.

We demonstrate how to fully ascribe Raman peaks simulated using ab initio molecular dynamics to specific vibrations in the structure at finite temperatures by means of Wannier functions. Here, we adopt our newly introduced method for the simulation of the Raman spectra in which the total polarizability of the system is expressed as a sum over Wannier polarizabilities. The assignment is then based on the calculation of partial Raman activities arising from self- and/or cross-correlations between different types of Wannier functions in the system. Different types of Wannier functions can be distinguished based on their spatial spread. To demonstrate the predictive power of this approach, we applied it to the case of a cyclohexane molecule in the gas phase and were able to fully assign the simulated Raman peaks.