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Atomic radius plays a key role in the realm of science to understand atomic/molecular physico-chemical properties. Looking at the enormous potential this descriptor has, a model is proposed for absolute radius (r) in terms of electrophilicity index (ω). Atomic radii for 103 elements of the periodic table are reported. Considering the periodic relationship between absolute radius and atomic electrophilicity, this empirical model is proposed invoking regression analysis. The computed radii obey sine qua non of periodic properties. Relativistic effects are also distinct in the newly computed radii. On comparison, the computed data is noted to be in close conformity with the reported radii. Further, some size-dependent properties are calculated by employing the computed absolute radius. These present a substantial periodic behaviour and association with absolute radii. [ABSTRACT FROM AUTHOR]

Ground and excited-state proton transfer and electrical responsive properties along the proton transfer co-ordinate of four donor–acceptor substituted pyrazole derivatives have been investigated using the density function-based range separated hybrid GGA functional ωB97XD with 6-311G(d) basis. Both intrinsic reaction coordinate (IRC) and distinguished co-ordinate (variation of O–H distance of the enol tautomer) have been chosen as a proton transfer co-ordinate of the titled compounds for comparison. Our study reveals that the various electrical responsive parameters like average polarizability (αav), first hyperpolarizability (βav) and global reactivity descriptors e.g., chemical hardness (η), electrophilicity index (ω) along the proton transfer co-ordinate are in conformity with the respective optimum principles. Maximum value of βav is found in the case of nitro substituted pyrazole derivative. Variation of βav along the proton transfer co-ordinate for all compounds have been correlated with the variation of Δµf0/(S1-S0)3 using two-level approximation and electronic special extent () along the proton transfer coordinate. [ABSTRACT FROM AUTHOR]

Recently, we have defined atomic polarizability, a Conceptual Density Functional Theory (CDFT)-based reactivity descriptor, through an empirical method. Though the method is empirical, it is competent enough to meet the criteria of periodic descriptors and exhibit relativistic effect. Since the atomic data are very accurate, we have applied them to determine molecular polarizability. Molecular polarizability is an electronic parameter and has an impact on chemical–biological interactions. Thus, it plays a pivotal role in explaining such interactions through Structure Activity Relationships (SAR). In the present work, we have explored the application of polarizability in the real field through investigation of chemical–biological interactions in terms of molecular polarizability. A Quantitative Structure–Activity Relationship (QSAR) model is constructed to account for electronic effects owing to polarizability in ligand–substrate interactions. The study involves the prediction of various biological activities in terms of minimum block concentration, relative biological response, inhibitory growth concentration or binding affinity. Superior results are presented for the predicted and observed activities which support the accuracy of the proposed polarizability-QSAR model. Further, the results are considered from a biological viewpoint in order to understand the mechanism of interactions. The study is performed to explore the efficacy of the computational model based on newly proposed polarizability and not to establish the finest QSAR. For future studies, it is suggested that the descriptor polarizability should be contrasted with the use of other drug-like descriptors. [ABSTRACT FROM AUTHOR]

The study considers diffraction radiation, which is excited when an electron moves near a cluster of two interacting subwavelength particles. The interaction is manifested in the fact that the radiation field from each particle is determined not only by the external field of the electron, but also by the field of the neighboring particle. Based on the obtained expressions for the radiation field, the function of cluster polarizability is determined. It characterizes the cluster response to the field of the electron as a whole. It is interesting that the obtained response function of the cluster to an external field, even in the framework of linear theory, generally depends on the external field itself. [ABSTRACT FROM AUTHOR]

Owing to its successful application to complex molecular systems, computational density functional theory (DFT) has been used to study the effect of an electric field on the molecular polarizability and HOMO-LUMO gap of 1-phenyl-4-{2-[(1s,4r)-4-pentylcyclohexyl]ethyl}benzene (1) and its fluoro-, chloro-, and cyano-derivatives, namely, 1-fluoro-4-(4-{2-[(1s,4r)-4-pentylcyclohexyl]ethyl}phenyl)benzene (2), 1-chloro-4-(4-{2-[(1s,4r)-4-pentylcyclohexyl]ethyl}phenyl)benzene (3), and 4-(4-{2-[(1s,4r)-4-pentylcyclohexyl]ethyl}phenyl)benzonitrile (4). These molecules belong to the family of nematic liquid crystals with three rings: two benzene and one cyclohexane. Furthermore, two DFT approaches, namely, B3LYP and M062X, have been used to examine the results obtained. This study reveals a remarkable feature: the polarizability of these molecules follows nearly a step function when varied with respect to the electric field. The 4-(4-{2-[(1s,4r)-4-pentylcyclohexyl]ethyl}phenyl)benzonitrile (4) polarizes more than all other derivatives, whereas 1-fluoro-4-(4-{2-[(1s,4r)-4-pentylcyclohexyl]ethyl}phenyl) benzene (2) has the widest stability region of them all. With the increase in the electric field, polarizability increases in a smooth manner until a point called here the shoot-up point at which polarizability switches to a higher value and remains nearly constant as the field increases further. However, beyond a certain value of the electric field, polarizability undergoes a steep fall. It is also found that the effective length (long molecular axis) of the molecule has a direct effect on its polarizability. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the effect of shape and size of core on the plasmonic response of spherical ZnO@Au core-shell nanostructures embedded in a passive host matrices of MgF2 within the framework of the qausistatic approximation. The absorption cross-section and local field enhancement factor of spherical ZnO@Au core-shell nanostructures are effectively studied by optimizing the parameters for a fixed composite diameter of 20 nm. In this two-layered core-shell nanostructures, four plasmonic resonances are found; the first two resonances associated with ZnO/Au and Au/MgF2 interfaces, whereas the third and fourth resonances are associated with the transverse and longitudinal modes, respectively. The peaks position and intensity of these resonances are varied by optimizing the shape and size of the core material. The tunability of the plasmon resonances of the composite systems enables it to exhibit very interesting material properties in a variety of applications extending from the visible to infrared spectral regions. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the effect of shape and size of core on the plasmonic response of spherical ZnO@Au core-shell nanostructures embedded in a passive host matrices of MgF2 within the framework of the qausistatic approximation. The absorption cross-section and local field enhancement factor of spherical ZnO@Au core-shell nanostructures are effectively studied by optimizing the parameters for a fixed composite diameter of 20 nm. In this two-layered core-shell nanostructures, four plasmonic resonances are found; the first two resonances associated with ZnO/Au and Au/MgF2 interfaces, whereas the third and fourth resonances are associated with the transverse and longitudinal modes, respectively. The peaks position and intensity of these resonances are varied by optimizing the shape and size of the core material. The tunability of the plasmon resonances of the composite systems enables it to exhibit very interesting material properties in a variety of applications extending from the visible to infrared spectral regions. [ABSTRACT FROM AUTHOR]

The calix[4]arene molecule, abbreviated as CX[4], is known by the four phenolic groups and a hydrophobic cavity able to enclose small molecules. The interactions between CX[4] and NO3, NO2, CO2, and N2 gas molecules have been studied. These guest species are placed inside and outside the cavity of the host molecule CX[4]. The formation of H-bonding has been deeply discussed based on the infrared spectrum and the polarizability analysis. Global and local indices have been calculated for a series of gas (NO3, NO2, CO2 and N2) in interaction with the CX[4] molecule to explain the electrophilic or nucleophilic activations in endo-vs. exo-cavity interaction zone. As expected, there is a correlation between the proposed global electrophilicity and global nucleophilicity together for an explanation of the chemo-selectivity region. Finally, the topological parameter analyses of the host-guests interactions have been estimated by using DFT calculations.

We have measured the polarizabilities of four families of molecules adsorbed to Au{111} surfaces, with structures ranging from fully saturated to fully conjugated, including single-molecule switches. Measured polarizabilities increase with increasing length and conjugation in the adsorbed molecules and are consistent with theoretical calculations. For single-molecule switches, the polarizability reflects the difference in substrate-molecule electronic coupling in the ON and OFF conductance states. Calculations suggest that the switch between the two conductance states is correlated with an oxidation state change in a nitro functional group in the switch molecules.

Abstract Background Betulinic acid (BA) is a natural triterpenoid compound and exhibits a wide range of biological and medicinal properties including anti-inflammatory activity. Therefore, this theoretical investigation is performed to evaluate (a) physicochemical properties such as acid dissociation constant (pKa), distribution coefficient (logD), partition coefficient (logP), aqueous solubility (logS), solvation free energy, dipole moment, polarizability, hyperpolarizability and different reactivity descriptors, (b) pharmacokinetic properties like human intestinal absorption (HIA), cellular permeability, skin permeability (PSkin), plasma protein binding (PPB), penetration of the blood brain barrier (BBB), (c) toxicological properties including mutagenicity, carcinogenicity, risk of inhibition of hERG gene and (d) molecular mechanism of anti-inflammatory action which will aid the development of analytical method and the synthesis of BA derivatives. Methods The physicochemical properties were calculated using MarvinSketch 15.6.29 and Gaussian 09 software package. The pharmacokinetic and toxicological properties were calculated on online server PreADMET. Further, the molecular docking study was conducted on AutoDock vina in PyRx 0.8. Results The aqueous solubility increased with increasing pH due to the ionization of BA leading to decrease in distribution coefficient. The solvation energies in water, dimethyl sulfoxide (DMSO), acetonitrile, n-octanol, chloroform and carbon tetrachloride were − 41.74 kJ/mol, − 53.80 kJ/mol, − 66.27 kJ/mol, − 69.64 kJ/mol, − 65.96 kJ/mol and − 60.13 kJ/mol, respectively. From the results of polarizability and softness, it was clear that BA is less stable and hence, kinetically more reactive in water. BA demonstrated good human intestinal absorption (HIA) and moderate cellular permeability. Further, BA also exhibited positive CNS activity due to high permeability through BBB. The toxicological study revealed that BA was a mutagenic compound but noncarcinogenic in mice model. Moreover, molecular docking study of BA with PLA2 revealed that BA interacts with GLY22 & GLY29 through hydrogen bond formation and LEU2, PHE5, HIS6, ALA17, ALA18, HIS47 and TYR51 through different types of hydrophobic interactions. The binding affinity of BA was − 41.00 kJ/mol which is comparable to the binding affinity of potent inhibitor 6-Phenyl-4(R)-(7-Phenyl-heptanoylamino)-hexanoic acid (BR4) (− 33.89 kJ/mol). Conclusions Our computed properties may assist the development of analytical method to assay BA or to develop BA derivatives with better pharmacokinetic and toxicological profile.

The molar refraction, polarizability, and refractive index for a series of monocarboxylic, dicarboxylic, and unsaturated monocarboxylic acids, having a symmetric or asymmetric structure, were investigated by the application of quantitative structure property relationship (QSPR) technique. We used a linear regression method and a single molecular descriptor, the ZEP topological index, calculated in a simple manner, with the help of weighted electronic distances, and also calculated on the basis of the chemical structure of the molecules. The high-quality performance and predictive ability of the QSPR models obtained were validated by means of specific validation techniques: y-randomization test, the leave-one-out cross validation procedure, and external validation. The investigated properties are well modeled (with r2 > 0.99) by the ZEP index, using the regression analysis as a statistical tool for developing reliable QSPR models. Our approach provides an alternative technique to the existing additive methods for predicting the molar refraction and polarizability of carboxylic acids, which is essentially based on the summation of atom and/or functional group contributions or bond contributions, and of some correction increments.

In the present study, we have prepared the [Ba(Nd0.075Ti0.85Nb0.075)O3]0.30–[(Na0.5Bi0.5)TiO3]0.70 ceramic through solid-state double sintering route. New equations which were proposed by us earlier were used to describe and model the electromechanical, AC and DC resistivity data. The activation energy for resonance and anti-resonance at 300 K is 30.28 and 30.11 meV; whereas the value is 38.32 and 38.91 meV at 448 K. The higher activation energy for AC conduction when compared to DC conduction is attributed to the fast vibration of charged polar and conducting species in response to the applied frequency, which requires more temperature. [ABSTRACT FROM AUTHOR]

Chemical bond is a ubiquitous and fundamental concept in chemistry, in which the overlap plays a defining role. By using a new approach based on localized molecular orbitals, the overlap properties, e.g., polarizability α ¯ OP , population pOP, intra J OP intra , and inter J OP inter repulsions, and density ρOP, of polyatomic systems were calculated, analyzed, and correlated. Several trends are shown for these properties, which are rationalized by the balance of some well-known effects, such as, electron donor/withdrawing character and electronegativity. The overlap properties of unusual bonds are also analyzed, revealing an OZn4(OOCH)6 structure with four equivalent Zn–O chemical bonds with overlap properties like the O–O bond in H2O2, while in protonated methane C H 5 + , it is observed that a CH3⋯ H 2 + bond pattern at the equilibrium structure changes to a C H 3 + ⋯H2 pattern upon dissociation. Charge-shift resonance energies, atom-in-molecule properties, and the lone-pair-bond-weakening effects are related to the overlap properties, which can provide alternative views and insights into chemical bonds. [ABSTRACT FROM AUTHOR]

In this paper, the structural, electronic, non-linear optical (NLO) properties and vibrational frequencies of 4-(methoxycarbonyl)-phenylboronic acid have been examined theoretically using ab initio Hartree-Fock (HF) and Density Functional Theory (DFT/B3LYP) methods applying the standard 6-311++G(d,p) basis set. ¹H- and 13C NMR chemical shifts are calculated by employing the direct implementation of the gauge including-atomic-orbital (GIAO) method at the B3LYP/6-311++G(d,p) and HF/6-31G(d) levels of the theory. There are two conformers, cis-trans(ct) and trans-cis (tc) for title molecule. The energy difference between ct and tc conformers of studied molecule are of 0.126 kcal/mol with B3LYP/6-311++G(d,p) and 0.138 kcal/mol with HF/6-311++G(d,p), respectively. The conformer ct is more stable than the conformer tc. Also, the energy gap differences between the highest occupied and the lowest unoccupied molecular orbitals, dipole moment, polarizability and first static hyperpolarizability are calculated as a function of both dihedral angle (C3-C4-C7-O3), between methoxycarbonyl group (CH3-O-CO-) and benzene ring, and dihedral angle (C2-C1-B-O1), between boronic acid group (-B(OH)2) and benzene ring. In the change of the energy gap and polarizability depending on dihedral angles, it is shown that the polarizabilities follow inverse relationship the energy gaps. [ABSTRACT FROM AUTHOR]

Li 3 Mg 2 (Nb 1-x W x)O 6+x/2 (0 ≤ x ≤ 0.08) ceramics were synthesized by the solid-state reaction route. The effects of W6+ substitution on the phase composition, microstructure and microwave dielectric properties of Li 3 Mg 2 NbO 6 ceramics were investigated systematically. The XRD results showed that all the samples formed a pure solid solution in the whole doping range. The SEM iamges and relative density revealed the dense structure of Li 3 Mg 2 (Nb 1-x W x)O 6+x/2 ceramics. The relationship between the crystal structure and dielectric properties of Li 3 Mg 2 (Nb 1-x W x)O 6+x/2 ceramics was researched through polarizability, average bond valence, and bond energy. The substitution of W6+ for Nb5+ in Li 3 Mg 2 (Nb 1-x W x)O 6+x/2 ceramics significantly promoted the Q × f values. In addition, the increase of W6+ content improved the thermal stability of the Li 3 Mg 2 (Nb 1-x W x)O 6+x/2 ceramics. The Li 3 Mg 2 (Nb 0.94 W 0.06)O 6.03 ceramics sintered at 1175 °C for 6h possessed excellent properties: ε r ~ 15.82, Q × f ~ 124,187 GHz, τ f ~ −18.28 ppm/°C. [ABSTRACT FROM AUTHOR]

An analysis has been made of the influence of the excitation of internal degrees of freedom of molecules on the refractive index (n – 1) under the conditions of high thermal nonequilibrium using the problem on relaxation of molecular nitrogen and oxygen behind the front of a strong shock wave as an example. It has been shown that the processes of vibrational relaxation and the processes of electronic translational relaxation and dissociation alike may exert a substantial influence on the refractive index of the gas. The change in the refractive index has been shown to occur primarily because of the change in the gas density in the course of these processes. Also, it has been found that a slight but detectable influence (about 1–2% for n – 1) on the refractive index is exerted by the change in the polarizability of the gas as a result of the change in vibrational temperatures of the mixture's molecules and due to the excitation of electronic states and the dissociation of the starting components. [ABSTRACT FROM AUTHOR]

The study of the vibrational dependence of H2O polarizability α is based on the comparison of experimental and calculated line shifts induced by argon, nitrogen, and air pressure in different H2O vibrational bands. The dependence of α on the internal coordinate θ, which describes large-amplitude bending vibration in the molecule, is expressed by a power series. The coefficients of the power series were selected so as to ensure the best agreement between the calculated matrix elements 〈ψn|α(θ)|ψn〉 and the polarizability values α(n) derived from the analysis of experimental H2O absorption line shifts in nν2 vibrational bands by nitrogen, oxygen, air, and argon pressure. The rotational contributions in the effective H2O polarizability are calculated and discussed. The α(θ) representation found is compared with ab initio calculations. [ABSTRACT FROM AUTHOR]

The hydraulic structures for the land reclamation needs and their operation are the objects of careful attention. The water-bearing earth dams of small height pose an extra danger, where the accident occurs the most often. Such facilities should be constantly monitored to prevent the dangerous incidents. The article discusses an alternative method for studying the filtration properties of earth dams by the electrical parameters - resistivity, induced polarization and self-potential. The relative polarizability was used to exclude the influence of electrical resistivity to the induced polarization data. A study of advanced technology to identify the filter zones was carried out on an earthen dam in the Almaty region, Kazakhstan. The measurement data for three profiles are presented as the sections form in the parameters of resistivity and relative polarizability. Their complex interpretation with the respect of self-potential data, is given as a diagram of probable filtration paths. This is possibly due to the local increased watering in the dam loamy body. Then, the electric and self-potential parameters were evaluated to determine the filtering zones. The study results of above parameters have identified several water-saturated zones in the dam body. This technology could be used to estimate the condition of such objects and their engineering-geological monitoring. [ABSTRACT FROM AUTHOR]

This study aims to decrease the dielectric constant of kraft paper by 1,2,3,4‐butanetetracarboxylic acid (BTCA) esterification crosslinking. Kraft paper samples are treated with various concentrations of BTCA to prepare modified paper with different reaction degrees. Morphology and surface chemical composition are characterized. The dielectric constant and loss of the plain and modified paper are also investigated. Results show that esterification occurs successfully between cellulose molecular chain and BTCA. The intrinsic dielectric constant and loss of 6 g L−1 BTCA‐treated paper decrease by 23.5% and 36.3%, respectively, at 50 Hz. The esterification can reduce the hydroxyl amounts on cellulose. The formed crosslinking network between the cellulose chains restricts the cellulose orientation polarization, thereby reducing cellulose polarizability. The electrical strength, mechanical properties, and thermal behavior of the samples are explored to evaluate comprehensively the modifying effect. BTCA esterification crosslinking proves to be a promising method for decreasing the dielectric constant of kraft paper. [ABSTRACT FROM AUTHOR]

Miniaturization of electronic gadgets continuously demands for the improved dielectric and flexible polymer composites. MXene flakes are considered as ideal electrically conductive 2D fillers inserted into the insulating polymer matrix to boost the dielectric performance of the polymer composites while maintaining superb flexibility. The present work is focused on the synthesis and characterization of strong and flexible PVC/MXene nanocomposites, possessing high dielectric constant and minimum energy loss, for their use in energy storage electronic applications. For this purpose, highly conductive delaminated MXene (DM) was prepared by HF-etching before delamination by DMSO and water and followed by high-temperature annealing. The prepared conducting DM was then inserted into insulating PVC in various concentrations by a simple solution casting method aided by strong sonication. The embedded DM in PVC facilitates the formation of conducting-insulating-conducting network CICN by increasing the AC conductivity of the obtained nanocomposites, which is explained according to the percolation theory. At the percolation threshold of 10 wt% MXene, the maximum number of PVC/MXene interfaces promotes interfacial polarization which endows the fabricated nanocomposites with high dielectric characteristics. The composite achieves a highest dielectric constant of 11800, which encompasses all the previous reported values. Also, low dielectric loss of 1.31 originates from the increase in electrical conductivity of the entire composite which in turn arises from the strong tunneling effect of conducting DM in PVC matrix. Moreover, thin films of the obtained composites also display very high flexibility, increased thermal conductivity of 3.48 W/mK, an extraordinary thermal stability (683.8 °C) and good mechanical stability, as the tensile strength reaches to 174.08%. Afterwards, the respective optimized nanocomposites were characterized by SEM, XRD and FTIR convincing the strong interfacial interaction and improved dispersion of DM flakes into PVC matrix. These unique features of our prepared PVC/MXene flexible thin films support their tremendous potential for modern dielectric applications. Image 1 [ABSTRACT FROM AUTHOR]

La[Al1−x(Mg0.5Ti0.5)x]O3 (LAMT, x = 0‐0.2) ceramics were synthesized by the conventional solid‐state reaction method and formed a solid solution. The pure solid solutions were recorded by X‐ray diffraction (XRD) in every range. Relative permittivity (εr) and structural stability were greatly affected because the Al3+ site was replaced by [Mg0.5Ti0.5]3+. The total ionic polarizability gradually increased with x, and εr gradually increased. The trend of τf is due to the change in structural stability. The variation in Q × f value increased firstly and then decreased due to the change in the symmetric stretching mode of Al/MgTi–O. The optimum microwave dielectric properties of LAMT were obtained at x of 0.1 after sintering at 1650°C for 5 hours, and εr = 24.9, Q × f = 79 956 GHz, and τf = −33 ppm/°C. The CaTiO3 have a large positive τf (+800 ppm/°C), thus, the τf achieved near zero when CaTiO3 and LAMT (x = 0.1) ceramics were mixed with a certain molar mass, and the optimum microwave dielectric properties of 0.65CaTiO3–0.35LaAl0.9(Mg0.5Ti0.5)0.1O3 were as follows: εr = 44.6, Q × f = 32 057 GHz, and τf = +2 ppm/°C. [ABSTRACT FROM AUTHOR]

The polarizability of endohedral complexes of fullerenes and fullerene hydrides with atoms of noble gases Ng@СN (N = 20, 24, 28, 30, 36, 50, 60, 70; X = He, Ne, Ar), Kr@СN (N = 28, 30, 36, 50, 60, 70), Xe@Сn (n = 50, 60, 70), C60Hn (n = 2, 6, 18, 36), and C20Hn (n = 2, 6, 12, 20) is studied by the PBE/3ζ level of density functional theory. It is established that the deviation of the calculated average polarizability of endohedral complexes from the additive scheme correlates with the change in the volumes of the СN and C20/60Hn fullerene cages upon encapsulation. The change in volume governs the absolute deviation of the average polarizability from additivity, while its sign depends on the direction of charge transfer in an endohedral complex. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Three models to compute the refractive index of gaseous mixtures at real gas conditions are presented with the purpose to improve the accuracy of state relationships between refractive index and thermodynamic properties. Models are compared with experimental data to determine one that is applicable to high pressure mixtures with non-ideal thermodynamic behavior near or above a fluids' critical point. The optimal model is applied to analyze adiabatic thermal mixing of fuel and air at typical diesel engine conditions. Results show that the ideal gas mixture law is appropriate in the vapor region, assuming it is known, for example, from experimental measurements. Finally, the model is applied for binary fuel-air mixing at supercritical conditions to demonstrate its full potential. [ABSTRACT FROM AUTHOR]

Structural features of moderate‐to‐strong O—H...O hydrogen bonds are related to the frequencies of O—H stretching vibrations and to the electric polarizability distribution in the donor and acceptor functional groups for crystals synthesized from the 1,2,4,5‐benzenetetracarboxylic (pyromellitic) acid, namely: bis(3‐aminopyridinium) dihydrogen pyromellitate tetrahydrate, (1); bis(3‐carboxypyridinium) dihydrogen pyromellitate, (2); bis(3‐carboxyphenylammonium) dihydrogen pyromellitate dihydrate, (3); and bis(4‐carboxyphenylammonium) dihydrogen pyromellitate, (4). A combination of single‐crystal X‐ray diffraction, powder Raman spectroscopy and first‐principle calculations in both crystalline and gaseous phases has shown that changes in the O—H...O hydrogen‐bond geometry can be followed by changes in the corresponding spectral modes. Vibrational properties of moderate hydrogen bonds can be estimated from correlations based on statistical analysis of several compounds [Novak (1974). Struct. Bond.18, 177–216]. However, frequencies related to very short O—H...O bonds can only be predicted by relationships built from a subset of structurally similar systems. Moreover, the way in which hydrogen bonds affect the polarizability of donor and acceptor groups depends on their strength. Moderate interactions enhance the polarizability and make it more anisotropic. Shorter hydrogen bonds may decrease the polarizability of a group as a consequence of the volume restraint implied by the neighbour molecule within a hydrogen‐bonded aggregate. This is significant for evaluation of the electric susceptibility in crystals and, therefore, for estimation of refractive indices and birefringence. [ABSTRACT FROM AUTHOR]

Atomic polarizability is an essential theoretical construct to define and correlate many physicochemical properties. It exhibits periodicity and has a relationship with other periodic descriptors. Although a number of scales are available to compute atomic polarizability, the final scale is yet to be designed. In this venture, we have invoked a new empirical approach to compute the atomic polarizability of 103 elements of the periodic table, considering the conjoint action of other periodic descriptors, namely effective nuclear charge (Zeff) and absolute radii (r). The proposed approach is α = a [ (r 3 / Z eff) e 2 ] + b , where "e" represents the electronic charge, Zeff is the effective nuclear charge, r is the absolute radius, and α is the polarizability. Our computed atomic polarizability follows all sine qua non of the periodicity. Our model significantly exhibits the relativistic effect too. A close agreement between our computed data and other available theoretical and experimental results demonstrates the efficacy of our proposed approach. Furthermore, we have established the polarizability equalization principle in terms of our computed data. [ABSTRACT FROM AUTHOR]

Glasses with compositions xTeO2 - (35-x) BaO - 65V2O5 (where x = 5, 10, 15, 20, 25 and 30 mol %) were prepared using a conventional melt quenching method. Densities of the glasses at room temperature were determined with the Archimedes method. The theoretical linear refractive index and optical band gap of the glasses were calculated by the Lorentz-Lorenz equation. The glasses possess high refractive index (2.16 - 2.19) and comparatively narrow band gap (3.9 - 4.1 eV). The third order nonlinear optical susceptibility X(3) was determined by generalized Miller’s rule. It was established that X(3) equal to 0.72 - 0.85x10-12 esu is close to the experimental value of ~10-12 esu measured for pure TeO2 glass and TeO2 containing glasses by other authors using THG method. The refractive index and third order nonlinear optical susceptibility decrease and band gap increases with increasing TeO2 content. The average single bond strength BM-O and the interaction parameter A of the glasses were calculated. It was shown that BM-O is in the 258 - 295 kJ/mol range and A is in the 0.050 - 0.055 À-3 range suggesting for the presence of week chemical bonds. VO5, VO4 and TeO3 structural units were confirmed by the IR spectra and structural models of the glasses containing Ba…O-V, V-O-V and V-O-Te bonds were proposed. The oxide ions in these bonds possess high polarizability giving main contribution to the high values of linear and nonlinear optical properties of the glasses. [ABSTRACT FROM AUTHOR]

Using the PBE/3ζ density functional theory method, we have computationally studied fullerene–1,4-dioxane adducts, which were recently synthesized in sonochemical reaction of C60/C70 with ethylene glycol in the presence of NaOH. We have found the preference of the boat conformations of C60 and C70 adducts with 1,4-dioxane over the chair ones. Fullerene–dioxane adducts have the dipole moments of 2.5–3.0 D and band gaps narrower as compared with original C60/C70. Adducts ab-, cc1-, and cc2-C72H4O2 are revealed higher stability than their regioisomers. Herewith, cc-adducts have the lower mean polarizabilities that corresponds to the experimental observation of the cc-functionalization of the C70 fullerene core. All adducts have the nonzero anisotropies of polarizability higher than the values of starting C60 and C70. The lowest anisotropy corresponds to cc1-C72H4O2 that makes this compound promising for organic solar cells. [ABSTRACT FROM AUTHOR]

In this article, we used density functional theory (DFT) to investigate the structural, electronic and nonlinear optical properties of N, P, As and Sb doped fullerene. The average polarizability and hyperpolarizability is significantly improved when these impurities are substituted individually in the (C60) lattice structure. The maximum hyperpolarizability is calculated for N-doped fullerene (3541.27 au) followed by P-doped fullerene (259.71 au), As-doped fullerene (102.52 au) and Sb-doped fullerene (32.06 au). A similar trend is observed and the polarizability is found to decrease monotonically. Both the polarizability and hyperpolarizability values are found to decrease with an increasing energy gap of the doped fullerene. N-Doped fullerene has the lowest energy gap (1.28 eV) followed by P-doped fullerene (1.94 eV), As-doped fullerene (2.02 eV) and Sb-doped fullerene (2.10 eV). The lowest energy gap minimizes the excitation energy and thus improves the nonlinear optical response. From the calculation of time-dependent-DFT (TD-DFT), it is observed that the maximum absorption wavelength of N-doped fullerene, which is about 830 nm, is shifted towards the longer wavelength at the infrared region in the case of P, As, and Sb-doped fullerenes. The results obtained through this study will help encourage the potential utilization of the metal-free doped-fullerene systems as a form of unique optical devices, thermal radiation detector, etc. [ABSTRACT FROM AUTHOR]

This essay focuses on general relations between the chemical structure and dipole polarizability of fullerenes (fullerenes themselves, their ions, exohedral derivatives, dimers, oligomers, and endohedral complexes). [ABSTRACT FROM AUTHOR]

Optical dipole traps emerged as a special case of what today we know as optical tweezers. They were first developed to trap neutral atoms, which posses a diameter much smaller than the wavelength of the trapping light. Due to its significance and applicability in cold atoms and molecules experiments, its comprehension becomes important. Therefore, in this work, we construct, step-by-step and didactically, the theoretical description of the optical dipole trap and one of its two possible regimes, the quasi-electrostatic trap (QUEST). We present one possible experimental setup, emphasizing the advantages of the optical dipole trap in the QUEST regime. [ABSTRACT FROM AUTHOR]

The effects of silver nanoparticles (Ag NPs) embedment on the physical and structural characteristics of the holmium ions (Ho3+) activated phosphate-based glass-ceramics were assessed. Two series of such glass-ceramics were prepared using the melt-quenching and characterized. In the first series, the Ag NPs were nucleated from the incorporated AgCl via the redox process. In the second series, the pure Ag nanopowder was directly added. The overall properties of these glass-ceramics were strongly sensitive to the cooling procedure and NPs addition strategies, leading to different density and refractive index modifications in the two series. The recorded O1s XPS peaks were exploited to determine the bridging to non-bridging oxygen ratios in the studied glass-ceramics network that enabled to unfold the differences in the observed inferences. A compelling correlation among various attributes in the achieved glass-ceramics was established. Briefly, the overall traits of the proposed glass-ceramics were tailored by regulating the preparation conditions. [ABSTRACT FROM AUTHOR]

The optical properties of dielectric nanostructures strongly depend on dielectric nanoparticles (NP) polarizability which can take the high values even interacting with low-intensity radiation. In this article, we are trying to find out if this is possible for electron transits to indirect exciton (IX) states at the NP surface. Because the exciton energy spectrum depends on NP shape and size, we research these factors influence on NP polarizability within the dipole approximation framework. For a quantitative assessment, we use a nanosystem containing a spherical dielectric alumina nanoparticle in a dielectric medium with a lower permittivity. We estimated the impact of NP size effect on the NP energy spectrum and the NP polarizability in case of exciton transitions to spatially separated electron and hole condition at the interface of dielectric nanoparticle and dielectric medium. Thus, using the variational method, we found that NP polarizability can achieve many orders of magnitude higher values than for atomic and molecular electron transitions case. It's take place for infrared, visible and ultraviolet radiation ranges. Also was found that size-dependence of IE energy spectrum weakly affects on NP polarizability. The obtained results can be used for creating the nano- and heterostructures for advanced nanophotonic applications that operate in conditions of weak optical fields. [ABSTRACT FROM AUTHOR]

The optical properties of an ensemble of metal nanoparticles coated with an oxide layer have been investigated within framework of the classical theory. The influence of the electron-scattering mechanisms on the polarizability of nanoparticles is analyzed. The limiting case of a thin oxide layer is considered, and analytical expressions for the real and imaginary parts of the polarizability are derived. The evolution of the frequency dependences of the polarizability and extinction coefficient upon variation in the particle size and oxide-layer thickness is investigated. It is shown that the consideration of the size dependence of the surface component of the relaxation time changes the character of the size dependence of the frequency of surface plasmons of two-layer nanoparticles. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the surface plasmon resonance of metallo-dielectric core-shell nanoparticle in the near-infrared (NIR) regime of the light. The wavelength-dependent permittivity of the metal has been deduced by the Lorentz-Drude (LD) model. We have analytically analyzed the polarizability and scattering cross-section of the core-shell nanoparticle in the NIR regime, i.e. 1400–3000 nm. The resonance has been attained due to the surface plasmon resonance (SPR) at the interface of the metal (with negative permittivity) and dielectric interface. Furthermore, the effects of core-shell radii on polarizability and scattering cross-section of core-shell nanoparticle have been taken up. It has been noticed that resonance can be altered by tailoring core-shell radii of the metallo-dielectric nanoparticle. Such a structure would be useful in integrated photonic applications. [ABSTRACT FROM AUTHOR]