Calculation Of Polarizabilities Research Articles

Molecular Polarizabilities in Aqueous Systems from First-Principles.

We discuss the results of first-principles calculations of molecular polarizabilities in condensed systems composed of well-defined building blocks, with a focus on water and simple aqueous solutions. We show that molecular polarizabilities are subtle fingerprints of structural changes induced in liquid water by the environment, e.g., the presence of ions and confined media, as well as by temperature and pressure. We also point out the importance of molecular polarizabilities in the calculation and interpretation of specific vibrational signatures of aqueous systems, notably Raman and sum-frequency generation spectra.

Describing polymer polarizability with localized orbital scaling correction in density functional theory.

Polarizability reflects the response of the molecular charge distribution to an applied external electric field and thus closely relates to the molecular electron density. For the calculation of polarizability within density functional theory (DFT), it is well known that conventional density functional approximations (DFAs) greatly overestimate the results for polymers with long chains and the π-conjugated system. This is a manifestation of the delocalization error of the commonly used DFAs-they normally produce too delocalized electron density and underestimate the total energy for systems with fractional charge character, which occurs for long molecules in a longitudinal electric field. Thus, to achieve an accurate description of polarizabilities for polymeric molecular systems from DFT, applying DFAs with minimal delocalization error is very important. In this work, we use the recently developed localized orbital scaling correction (LOSC) to the conventional DFAs, which has been shown to largely eliminate the delocalization error, to calculate and study the polarizabilities of three classic polymers, polyyne, polyacetylene, and hydrogen chain. The results from this work demonstrate that applying LOSC to conventional DFAs with self-consistent field calculations can largely improve the description of polarizability from DFT calculations and the improved quality of electron density in LOSC leads to the improved results of polarizability of the polymers. However, the improvement is not complete and adjustment of the parameters in the LOSC method can further improve the accuracy to reach the level similar to the MP2 method. This work also points to the direction for the further development of LOSC in self-consistent calculations.

Static dipole polarizabilities of atoms and ions from Z = 1 to 20 calculated within a single theoretical scheme

Static dipole polarizabilities for the first 20 atoms and ions of the Periodic Table are calculated within a single theoretical scheme: the coupled-cluster method with a Hartree–Fock reference wavefunction using an augmented-polarization-consistent and polarization-consistent basis set. The values of the atomic polarizabilities of neutral atoms obtained here agree extremely well with the experimentally measured values. For the ions, all the calculations are consistent with experimental values with the highest resolution so far, except for the monovalent calcium ion, probably due to strong relativistic effects. To the best of our knowledge, this is the first time, applying a single theoretical scheme successfully predicts static polarizabilities of all 20 consecutive elements across 8 columns and more than 3 full periods being consistent with the experimentally measured values both for neutrals and ions. The results clearly signal the universality of this theoretical scheme for the atomic polarizability calculation, and should be easy to extend to other elements with weak relativistic effects. We adopt the CCSD(T) method with an augmented polarization-consistent and polarization-consistent basis set to calculate the atomic and ionic polarizabilities for the first 20 atoms and ions of the Periodic Table. Our calculation results are in good agreement with the experimental data with the highest accuracy so far and the reported high accuracy calculation results. Semi-logarithm plot of calculated static polarizabilities of neutral atoms (filled circles, black line) and ions (open circles). The colored lines join isoelectronic species.

Calculations of atomic polarizability for beryllium using MCDHF method* *Project supported by the National Key Research and Development Program of China (Grant No. 2017YFA0402300), the National Natural Science Foundation of China (Grant Nos. 11774292, 11804280, 11874051, and 11864036), the Scientific Research Funding of the Higher Education Institutions of Gansu Province of China (Grant No. 2018A-002), and the Major Project of

Based on the fully relativistic multiconfiguration Dirac–Hartree–Fock (MCDHF) method and the corresponding program package GRASP2018, a new program for calculating the polarizabilities is developed. As the first application, the static electric-dipole polarizabilities of the ground state 2s2 1 S 0 and excited state 2s2p 3 P 0 of beryllium are calculated. By means of these polarizabilities, the blackbody radiation (BBR) shift of the 2s2p 3 P 0 → 2s2 1 S 0 clock transition is determined. The present results agree very well with other available theoretical results.

Synthesis and Controllable Growth Dynamics of Third Order Nonlinear Optical Material of 2-Amino-4-Methylpyridinium 2-Chloro 4-Nitro Benzoate Electro-Mechanical Investigation and Device Fabrication

An organic nonlinear optical material 2-Amino-4-methylpyridinium 2-chloro 4-nitro benzoate (AMPCNB) was synthesized and large size single crystals were grown by slow evaporation solution growth method. Single crystal X-ray diffraction study showed that the title compound belongs to monoclinic crystal system with P21/n space group. A powder XRD study was performed to ascertain its phase. The UV–VIS-NIR study was performed to investigate the transparency window and lower cutoff wavelength of the compound, no absorption has been observed between 318 and 1100 nm. The third harmonic efficiency of the title compound has been studied using the Z-scan technique using continuous-wave Nd:YAG laser to confirm its saturable absorption and self-defocusing effect. The photo conducting and charge transport properties are analyzed using photoconductivity and dielectric measurements. Theoretical calculation of molecular polarizability, which is helpful in device fabrication, was carried out from Penn gap, Clausius-Mosotti equations and the obtained results were compared. Mechanical properties of the grown crystal were investigated by Vicker’s microhardness study.

Dipole-dipole polarizability of the cadmium -=SUP=-1-=/SUP=-S-=SUB=-0-=/SUB=- state revisited -=SUP=-*-=/SUP=-

Experimental results and high-level quantum chemical ab initio calculations of the static polarizability α=α(ω=0)) of the cadmium 1S0 state are still in marked disagreement. Here we analyze this discrepancy by using experimentally determined dipole oscillator strength distributions (DOSD). It will be shown that within this procedure the experimentally determined static polarizability α0 will shift from 49.7± 1.6 au to considerably lower values. We now conclude an experimentally determined polarizability of α0 = 47.5 ± 2.0 au in much better agreement with the latest calculations of α0~ 46 au. Keywords: cadmium, polarizability, DOSD

Динамическая поляризуемость отрицательного иона водорода

We performed the calculations of the frequency-dependent polarizability of a hydrogen anion by using correlation-consistent basis sets with high diffuseness. The results obtained turned out to be close to the results obtained by the method of summation over pseudo-states. It is also shown that calculations by the density functional method do not allow obtaining high accuracy. This is due to the large size of anions compared to both cations and neutral atoms (molecules).

Removing artifacts in polarizable embedding calculations of one- and two-photon absorption spectra of fluorescent proteins.

The multiscale calculations involving excited states may suffer from the electron spill-out (ESO) problem. This seems to be especially the case when the environment of the core region, described with the electronic structure method, is approximated by a polarizable force field. The ESO effect often leads to incorrect physical character of electronic excitations, spreading outside the quantum region, which, in turn, results in erroneous absorption spectra. In this work, we investigate means to remove the artifacts in one-photon absorption (OPA) and two-photon absorption (TPA) spectra of green and yellow fluorescent protein representatives. This includes (i) using different basis sets, (ii) extending the core subsystem beyond the chromophore, (iii) modification of polarization interaction between the core region and its environment, and (iv) including the Pauli repulsion through effective core potentials (ECPs). Our results clearly show that ESO is observed when diffuse functions are used to assemble the multielectron wave function regardless of the exchange-correlation functional used. Furthermore, extending the core region, thus accounting for exchange interactions between the chromophore and its environment, leads to even more spurious excited states. Also, damping the interactions between the core subsystem and the polarizable force field is hardly helpful. In contrast, placing ECPs in the position of sites creating the embedding potential leads to the removal of artificious excited states that presumably should not be observed in the OPA and TPA spectra. We prove that it is a reliable and cost-effective approach for systems where the covalent bond(s) between the core region and its environment must be cut.

Calculation of Polarizabilities for Atoms with Open Shells

A version of the configuration interaction method for atoms with open shells (the Configuration Interaction with Perturbation Theory—CIPT method, PRA 95, 012503 (2017)) is extended for calculation of static and dynamic polarizabilities. Its use is demonstrated by calculation of the polarizabilities for the ground and excited states of Er, Tm and Yb. It is proved to be an useful tool in designing a new generation of optical atomic clocks sensitive to new physics.

Scattering and Its Applications to Various Atomic Processes: Elastic Scattering, Resonances, Photoabsorption, Rydberg States, and Opacity of the Atmosphere of the Sun and Stellar Objects

A scattering process can be a natural process or a process carried out in a laboratory. The scattering of particles from targets has resulted in important discoveries in physics. We discuss various scattering theories of electrons and positrons and their applications to elastic scattering, resonances, photoabsorption, excitation, and solar and stellar atmospheres. Among the most commonly employed approaches are the Kohn variational principle, close-coupling approximation, method of polarized orbitals, R-matrix formulation, and hybrid theory. In every formulation, an attempt is made to include exchange, long-range and short-range correlations, and to make the approach variationally correct. The present formulation, namely, hybrid theory, which is discussed in greater detail compared to other approximations, includes exchange, long-range correlations, and short-range correlations at the same time, and is variationally correct. It was applied to calculate the phase shifts for elastic scattering, the resonance parameters of two-electron systems, photoabsorption in two-electron systems, excitation of atomic hydrogen by an electron and positron impact, and to study the opacity of the Sun’s atmosphere. Calculations of polarizabilities, Rydberg states, and bound states of atoms are also discussed.

A computational quantum chemical and polarizability calculations of liquid crystal 4-cyano-4-pentylbiphenyl with water molecule (H2O)

In this paper, we investigate the quantum chemical parameters such as energy of the highest occupied molecular orbital (EHOMO), energy of the lowest unoccupied molecular orbital (ELUMO), HOMO-LUMO energy gap (△Egap), ionization potential (I), electron affinity (A), chemical potential (μ), electronegativity (χ), hardness (η), softness (S), and electrophilicity index (ω) of liquid crystal (LC) 4-cyano-4-pentylbiphenyl with water molecule (H2O). Above quantum chemical parameters have been calculated at Becke's three-parameter hybrid exchange functional and the Lee–Yang–Parr correlation functional (B3LYP) with 6-31G(d) and 6-31G++(d,p) basis sets in the framework of density-functional theory (DFT). For comparative purposes, we also optimize 4-cyano-4-pentylbiphenyl with water molecule at Perdew-Burke-Ernzerhof (PBEPBE) with 6-31++G(d,p) level. Mulliken charge analysis infer that (-0.03e) amount of charge is being associated with the H2O at B3LYP/6-31G(d) level. This fact indicates a considerable amount of electron population is transferred from pristine 4-cyano-4- pentylbiphenyl to H2O molecule. Polarizability tensor components such as αxx, αyy, αzz, average polarizability (αav), and polarizability anisotropy (Δα) have been calculated. The most intense IR spectral characteristics of 4-cyano-4-pentylbiphenyl with water molecule are accommodated in between 3000 cm−1 to 3920 cm−1at all presented levels.

Thermoelectric and Plasmonic Properties of Metal Nanoparticles Linked by Conductive Molecular Bridges

Thermoelectric and plasmonic properties of systems comprising small golden nanoparticles (NPs) linked by narrow conductive polymer bridges are studied using the original hybrid quantum‐classical model. The bridges are considered here to be either conjugated polyacetylene, polypyrrole, or polythiophene chain molecules terminated by thiol groups. The parameters required for the model are obtained using density functional theory and density functional tight‐binding simulations. Charge‐transfer plasmons in the considered dumbbell structures are found to possess frequency in the infrared region for all considered molecular linkers. The appearance of plasmon vibrations and the existence of charge flow through the conductive molecule, with manifestation of quantum properties, are confirmed using frequency‐dependent polarizability calculations implemented in the coupled perturbed Kohn–Sham method. To study the thermoelectric properties of the 1D periodical systems, a universal equation for the Seebeck coefficient is derived. The phonon part of the thermal conductivity for the periodical – system is calculated by the classical molecular dynamics. The thermoelectric figure of merit ZT is calculated by considering the electrical quantum conductivity of the systems in the ballistic regime. It is shown that for nanoparticles connected by polyacetylene, polypyrrole, or polythiophene chains at T = 300 K, the ZT value is {0.08;0.45;0.40}, respectively.

Dielectric properties, polarizability and molar refractive index of some VSrFeZnO glasses

Dielectric properties of a set of glasses having the composition (70-x)%V2O5 - x%ZnO − 10%SrO − 20%FeO is studied in terms of their permittivity and electric modulus. The dielectric data are collected at the frequencies 120, 103, 104 and 105 Hz and in the temperature range 300 − 523 K. The electric moduli are treated with different theoretical models. Good fitting to the experimental data are obtained with Cole–Cole and Davidson–Cole equations. The static relaxation time τ0 values are found to vary between 7.6x10−9 sec and 22.7x10−9 sec, and the parameters α and γ are found to be (α = 0.056 − 0.065) and (γ = 0.94 − 0.95). The calculated optical basicity values are found to decrease with increasing the %ZnO. The molar refractive index is found to be between 2.6 and 3.2. The calculated single bond strength values suggest the transfer of bond nature from the covalent to the ionic form. The obtained third-order nonlinear optical susceptibility χ(3) results and electronic polarizability calculations suggests these glasses to be good nominees for nonlinear optical applications.

Synthesis, physicochemical properties and computational study of donor–acceptor polymer for optical limiting application

A new donor–acceptor configured π-conjugated polymer P1 with alkoxy pendant groups having cyclic diimide and thiophene core moieties in polymer backbone were efficiently synthesized via polycondensation reaction. The incorporation of cyclic diimide in polymer increased the rigidity and thermal stability of polymer backbone aided by its high Tg value. These chromophores assisted in reducing the steric interaction of bulky alkoxy pendants which supported lowering the bandgap. The donor and acceptor moieties along with π spacers were particularly chosen to enhance the π-conjugation length in the polymer thereby increasing its nonlinear optical absorption i.e. two-photon absorption. The various structure–property relationships of the polymer were characterized by UV–Vis absorption, fluorescence emission, cyclic voltammetry, and density functional theory studies. The molecular nonlinear properties were theoretically evaluated through the calculation of polarizabilities and hyperpolarizabilities using time-dependent Hartree–Fock method. The polymer showed enhanced effective two-photon absorption with an absorption coefficient ( $$\beta_{eff}$$ ) of 2.031 × 10−10 m/W obtained from open aperture Z-scan analysis which is in good agreement with theoretical study.

Assessment of the proposed pseudo-potential theoretical model for the static and dynamic Raman scattering intensities: Multivariate statistical approach to quantum-chemistry protocols.

Accurate calculation of molecular polarizabilities and Raman intensities required high-level correlated wave functions (CCSD) and large basis set with the inclusion of electronic correlation within experimental precision. These requirements, in terms of time and computation, are economically costly. Polarized Gaussian basis sets adapted to effective core potentials (ECPs) for the static and frequency dependent Raman intensities is presented. The results of the proposed basis sets at CCSD and DFT levels in comparison with Sadlej-pVTZ, as reference basis set, show quite a good quantitative agreement in the properties with a valuable reduction in the computational time and resources. Multivariate principal component analysis (PCA) was performed to study the assessment of the efficiency of proposed methodology and diagnose the inherent information related to the kind of normal vibrational mode of each molecule, based on the variations in the computed Raman intensities. The results, in the form of score-plots, explored a clear segregation and classification among the Raman intensities data, revealing its dependence on the excitation frequencies of laser and nature of the vibrational mode of each molecule of interest. Moreover, the projection of the loadings-plots of the PCs successfully enabled to classify the most correlated computational methods in to the same groups, and made isolations of the less efficient basis functions at the corresponding theoretical method.

Overlap integrals and excitation energies calculations in trivalent lanthanides 4f orbitals in pairs Ln-L (L = Ln, N, O, F, P, S, Cl, Se, Br, and I)

In this work, DFT-based calculations of overlap integrals (ρ) and excitations energies (Δε) associated with the diatomic-like pairs Ln3+-Ligand and Ln-Ln’ are presented. The ρ and Δε quantities are useful for the calculations of overlap polarizability, charge factors, intensity parameters (using the Simple Overlap and Bond Overlap models), 4f shielding factors, and energy transfer process (ligand-to-Ln and Ln-Ln). A comprehensive set of parametric curves of the type exp(a + bR + cR2) are presented to easily determine these properties at a given distance R. Some literature is presented to indicate the importance of ρ and Δε quantities in photophysical properties of lanthanide-based compounds.

Accurate calculation of multipole polarizabilities for one-electron atom in Debye plasmas

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 2l-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 2l-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.

Origin of the Kerr effect: investigation of solutions by polarization-dependent Z-scan

The nonlinear refractive index dependence on the incident light polarization state has been studied for pure chloroform and chloroform solutions of aminobenziliden-1,3-indandione derivatives. Measurements were done with linearly, elliptically, and circularly polarized light using 8 ns and 30 ps pulse duration 1064 nm lasers. This allows us to separate the electronic response, molecular reorientation, and thermo-optical components of the nonlinear refractive index. The refractive index variations with the change of laser pulse repetition rate were employed to identify the presence of the thermo-optical effect. Quantum chemical calculations of linear polarizability were used to estimate the magnitude of molecular-reorientation-induced refractive index changes for solvents and solutions. Overall, in this paper we have outlined various essential aspects that need to be taken into account to correctly interpret Z-scan measurement results for organic solvents and solutions.

Simplified Ab Initio Molecular Dynamics-Based Raman Spectral Simulations.

We describe a simplified approach to simulating Raman spectra from ab initio molecular dynamics (AIMD) calculations. The protocol relies on on-the-fly calculations of approximate molecular polarizabilities using the well-known sum over orbitals (as opposed to states) method. This approach bypasses the more accurate but computationally expensive approach to calculating molecular polarizabilities along AIMD trajectories, i.e., solving the coupled perturbed Hartree-Fock/Kohn-Sham equations. We demonstrate the advantages and limitations of our method through a few case studies targeting molecular systems of interest to surface- and/or tip-enhanced Raman spectroscopy practitioners.

Synthesis, characterizations, crystal structures, and theoretical studies of copper(II) and nickel(II) coordination complexes

In the present study, we report synthesis, characterization, structural and theoretical studies of two copper(II) complexes, [Cu(py)2(L1)2] (1) and [Cu(phen)(Ac)2-Cu2(Ac)4]n (2), and a nickel(II) complex, [Ni(bipy)(L)(Ac)] (3), where py = pyridine, L1 = 3,5-dichloro-2-hydroxybenzaldehyde, phen = 1,10-phenanthroline, Ac = acetate ion, bipy = 2,2’-bipyridine and HL = 4-bromo-2-(Z)-(naphthalene-2-ylimino)methyl) phenol. The new complexes were fully characterized using microanalysis, FAB-mas (m/z), FT-IR, UV-Vis and fluorescence spectra, X-band EPR spectroscopy and then by single crystal X-ray diffraction studies. X-ray studies of 1 and 3 revealed distorted octahedral geometries. Complex 2 is a coordination polymer built by an octahedral copper unit Cu(phen)(Ac)2 alternating with paddle wheel species Cu2(Ac)4, located on a crystallographic center of symmetry, where an acetate anion bridges the two crystallographic independent copper ions. The fluorescence intensities and quantum yields of 1 and 2 were found to be more compared to 3. The preliminary tests in the potential application for theoretical biological activities of compounds have also been studied. Furthermore, we also performed quantum chemical calculations to get insights into the structure-property relationships of the synthesized complexes. The quantum chemical calculations were used for theoretical calculations of linear polarizability and third-order nonlinear optical polarizability (γ) for 1, 2 and 3. Besides this, the theoretical calculations, including the analysis of frontier molecular orbitals and electrostatic potential diagrams, are used to highlight the theoretical aspects of metal to ligand charge transfer (MLCT) processes in the studied complexes.