Vibrational Hyperpolarizabilities Research Articles

Superalkali-alkaline earthide ion pairs of δ+(AM-HMHC)-AM'δ- (AM = Li, Na and K; AM' = Be, Mg and Ca) possessing large NLO responses and excellent electronic stabilities and alkalide characteristics: a DFT study.

To identify superalkali-alkaline earthide ion pairs, it's theoretically shown that, as a novel class of excess electron superalkali compounds, both chair and boat forms of (AM-HMHC)-AM' (AM = Li, Na, and K; AM' = Be, Mg, and Ca; HMHC = 1,4,7,10,13,16-hexamethyl-1,4,7,10,13,16-hexaazacyclooctadecane) are good candidates. An attractive superalkali-alkaline earthide ion pair in δ+(AM-HMHC)-AM'δ- is firstly exhibited, which possesses alkaline-earthide characteristics and nonlinear optical response superior to similar M+(calix[4]pyrrole)M'- (M = Li, Na, and K; M' = Be, Mg, and Ca) with high stability. The electronic and vibrational second order hyperpolarizabilities and the frequency-dependent first hyperpolarizabilities of δ+(AM-HMHC)-AM'δ- are presented. For each pair of (AM-HMHC)-AM', the boat conformation is preferred to its chair one in the case of Hyper-Rayleigh scattering response (βHRS). These alkaline earthides suggest prominently high βHRS up to 2.59 × 104 a.u. (boat forms of δ+(Na-HMHC)-Caδ-). We expect that this work will inspire the preparation and characterization of these new alkaline earthides as high-performance NLO materials.

Alkaline earth metal Atom-Doped Aza-Single-Strand pyridine Helix M@SP-Helix (M = Be, Mg, and Ca) as high-performance candidates for Single-Molecular redox SPDT NLO molecular switches

Redox molecular switch is undoubted to be a good choice for the requirement of terminal molecular device. By doping an alkaline earth metal atom into the aza-single-strand pyridine helical ligand to form M@SP-Helix (M = Be, Mg, and Ca), the alkaline earth metal atom not only act the role of providing two electrons but also the type of them can significantly affect the distribution region of every two electrons on SP-Helix in the in the redox process. Our results found that the electronic and vibrational static first hyperpolarizabilities as well as the frequency-dependent first hyperpolarizability exhibit high-performance single-pole double-throw (SPDT) nonlinear optics (NLO) switching effects from its oxidized state (off form) to neutral (on form) and to reduced states (on form) as obtaining four electrons by twice. Notably, the electronic first hyperpolarizability is increased approximately 1003- and 1.34 × 106-fold from 35 to 3.51 × 104 and 4.69 × 107 au for Ca@SP-Helix. Therefore, this work can provide a theoretical reference that the alkaline earth atom doping is an important method to design high-performance NLO molecular switch material.

Vibrational and nonlinear optical properties of amine-capped push-pull polyynes by infrared and Raman spectroscopy

The vibrational properties of a series of push-pull polyynes have been studied by infrared and Raman spectroscopy. The simultaneous activation of a strong infrared and Raman mode, i.e. the collective vibration of CC bonds of the sp carbon chain, highlights the effectiveness of a polyyne bridge in promoting charge transfer between the electron donor (D) and acceptor (A) ends, thus suggesting that ad-hoc functionalized polyynes are worth being explored as building blocks of organic materials with attractive first-order optical nonlinearity. The optical, electronic, and vibrational properties of these molecules have been investigated with the support of density functional theory calculations, as well as the electronic and vibrational first hyperpolarizabilities ($\beta$). The mid-low region of the IR spectra (800-1600 cm$^{-1}$) has been analyzed in detail, searching for marker bands of the specific terminations of the different sp carbon chains thus achieving a complete vibrational characterization of sp hybridized push-pull systems.

Electronic and vibrational hyperpolarizabilities of alkali‐ and alkaline‐earth‐doped boron nitride nanotubes

AbstractThis work reports the results of the vibrational corrections and frequency dependence to the first hyperpolarizabilities of the alkali‐ and alkaline‐earth‐doped boron nitride nanotubes. The electronic contributions were computed by means of the density functional theory with the M06‐2X functional, and the vibrational corrections were calculated using the perturbation theoretical method and the field‐induced coordinates methodology. The results for the electronic contribution show that such materials exhibit large first hyperpolarizabilities and electride characteristic. We also show that the distribution of the excess electron, which originates from the doping atoms, plays an important role in the large electronic hyperpolarizabilities (βel). Moreover, our findings strongly indicate that the effect of vibrations on the hyperpolarizabilities can be quite important and can even be much larger than the electronic counterpart.

Computational analysis of vibrational spectroscopic properties and hyperpolarizability of silver adsorbed organic molecule, N,N' Dimethyl Urea Ninhydrin.

The effect of adsorption of silver atoms to the nonlinear optical (NLO) active compound N,N' dimethyl urea ninhydrin (NDUN), has been analysed by computational methods. Single, double or triple silver atoms are added to the NDUN structure at an appropriate site and the geometry optimization, vibrational spectral and the natural bond orbital analyses, and hyperpolarizability calculations are done using B3LYP functional with LANL2DZ basis set. A comparison of IR spectra of the Ag-adsorbed NDUN (NDUN-Ag) is made to study the effect of the addition of silver atoms in the vibrational motions of the molecule. The NBO analysis gives an account of the interactions between atoms of the chosen molecule. The effect on NLO properties of NDUN is characterized by the polarizability, and the first and the second hyperpolarizability calculations.

Can Density Functional Theory Be Trusted for High-Order Electric Properties? The Case of Hydrogen-Bonded Complexes.

This work reports on an extensive assessment of the performance of a wide palette of density functional approximations in predicting the (high-order) electric properties of hydrogen-bonded complexes. To this end, we compute the electronic and vibrational contributions to the electric polarizability and the first and second hyperpolarizabilities, using the CCSD(T)/aug-cc-pVTZ level of theory as reference. For all the studied properties, the average absolute errors below 20% can only be obtained using the CAM-B3LYP functional, while LC-BLYP and MN15 are shown to be only slightly less accurate (average absolute errors not exceeding 30%). Among Minnesota density functionals, i.e., M06, M06-2X, and MN15, we only recommend the latter one, which quite accurately predicts the electronic and vibrational (hyper)polarizabilities. We also analyze the optimal tuning of the range-separation parameter μ for the LC-BLYP functional, finding that this approach does not bring any systematic improvement in the predictions of electronic and vibrational (hyper)polarizabilities and the accuracy of computed properties is largely system-dependent. Finally, we report huge errors in predicting the vibrational second hyperpolarizability by ωB97X, M06, and M06-2X functionals. Based on the explicit evaluation of anharmonic terms contributing to the second hyperpolarizability, this failure is traced down to a poor determination of third- and fourth-order energy derivatives with respect to normal modes. These results reveal serious flaws of some density functional approximations and suggest caution in selecting the appropriate functional to calculate not only electronic and vibrational (hyper)polarizabilities but also other molecular properties that contain vibrational anharmonic contributions.

Molecular Docking and Comparative Vibrational Spectroscopic Analysis, HOMO-LUMO, Polarizabilities, and Hyperpolarizabilities of N-(4-Bromophenyl)-4-Nitrobenzamide by Different DFT (B3LYP, B3PW91, and MPW1PW91) Methods

We have recorded and analyzed FTIR and FT-Raman spectra of N-(4-Bromophenyl)-4-nitrobenzamide. Here, we have presented a comparative study between different method combinations. Firstly, we have done its geometry optimization. After this, we have calculated fundamental vibrational frequencies with intensity using different methods like B3PW91, MPW1PW91, and B3LYP/6-311G (d, p). The complete vibrational assignments of wavenumbers are made on the basis of potential energy distribution (PED). The result from the calculated spectra of the title compound shows excellent agreement with experimental spectra. We have also computed HOMO-LUMO gap and plotted frontier orbital HOMO-LUMO surfaces, Molecular electrostatic potential surfaces to explain the reactive nature of N-(4-bromophenyl)-4-nitrobenzamide. The values of hyper polarizability show a probable use of these compounds in electro-optical applications. From the result of docking picture, we can say that this compound effectively act as an antibacterial drug.

A Density Functional Theory Study on Nonlinear Optical Properties of Double Cage Excess Electron Compounds: Theoretically Design M[Cu(Ag)@(NH3 )n ](M = Be, Mg and Ca; n = 1-3).

In this work, we investigated the nonlinear optical (NLO) properties of excess electron electride molecules of M[Cu(Ag)@(NH3 )n ](M = Be, Mg and Ca; n = 1-3) using density functional theory (DFT). This electride molecules consist of an alkaline-earth (Be, Mg and Ca) together with transition metal (Cu and Ag) doped in NH3 cluster. The natural population analysis of charge and their highest occupied molecular orbital suggests that the M[Cu(Ag)@(NH3 )n ] compound has excess electron like alkaline-earth metal form double cage electrides molecules, which exhibit a large static first hyperpolarizability ( ) (electron contribution part) and one of which owns a peak value of 216,938 (a.u.) for Be[Ag@(NH3 )2 ] and vibrational harmonic first hyperpolarizability ( ) (nuclear contribution part) values and the ratio of / , namely, η values from 0.02 for Be[Ag@(NH3 )] to 0.757 for Mg[Ag@(NH3 )3 ]. The electron density contribution in different regions on values mainly come from alkaline-earth and transition metal atoms by first hyperpolarizability density analysis, and also explains the reason why values are positive and negative. Moreover, the frequency-dependent values β(-2ω,ω,ω) are also estimated to make a comparison with experimental measures. © 2018 Wiley Periodicals, Inc.

Electronic and Vibrational Hyperpolarizabilities of Lithium Substituted (Aza)benzenes and (Aza)naphthalenes

In this article we report results for the electronic and vibrational hyperpolarizabilities of ten molecules: Li@benzene, Li@pyridine, Li@pyrimidine, and Li@pyrazine; Li@naphthalene, Li@quinoline, Li@isoquinoline, Li@cinnolin, Li@quinazoline, and Li@quinoxaline. An electron correlation study shows that second-order many-body perturbation theory and density functional theory with CAM-B3LYP and M05-2X functionals give results for the electronic hyperpolarizabilities in good agreement with coupled cluster with single and doubles reference values. Static and dynamic vibrational corrections were computed through the perturbation theoretical method of Bishop and Kirtman and using a variational approach. In general, we obtained notable discrepancies between the results obtained by the two methods for the pure vibrational corrections because of the deficiency of the perturbation method to properly treat low-frequency normal modes present in the investigated systems. However, both methods give results similar to the zero-point vibrational average corrections.

Spectroscopic and non-linear optical studies of two novel optical limiters from dichloroaniline family crystals: 3,4-Dichloroaniline and 3,5-dichloroaniline

Two organic crystals of the isomeric forms of dichloroanilines such as 3, 4-dichloroaniline (3,4-DCA) and 3, 5-dichloroaniline (3,5-DCA) were grown by slow evaporation method and characterized by various analytical techniques. The vibrational normal modes of the samples were theoretically predicted using the scaled quantum mechanical force field procedures with the DFT level calculation and the potential energy distributions of the individual modes were estimated using the normal coordinate analysis. Fermi doublets and Evans holes were identified in the vibrational spectra of samples. The nuclear relaxation contribution to the vibrational polarizabilities and hyperpolarizabilities for the normal modes of the molecules were quantitatively estimated using the DFT method. The results of the calculated NLO responses showed that the vibrational mean contributions to the static polarizabilities and hyperpolarizabilities were smaller than the corresponding electronic contributions for the molecules. The Kurtz and Perry powder SHG efficiencies were measured and both samples have generated the second-harmonics of the fundamentals. The open-aperture Z-scan study results proposed the superior optical limiting property of 3,5-DCA with respect to 3,4-DCA.

Electronic and vibrational second hyperpolarizabilities of (MgO)n clusters.

In this work, we report results for the static second hyperpolarizability of magnesium oxide clusters including electronic and vibrational contributions. The comparison between second-order Møller-Plesset (MP2) perturbation theory and coupled cluster results to the electronic contribution points out that MP2 is a suitable method to compute this property. When computed at the MP2 level, the electronic contribution per atom converges to approximately 5000 a.u. Vibrational corrections were computed at the MP2 level through the perturbation theoretical method of Bishop and Kirtman. Results obtained showed that the term [α2]0,0 represents around 20% of the electronic counterpart while the term [μβ]0,0 is comparable to it. Modes that contribute significantly to [α2]0,0 are those in which all or part of the bond lengths simultaneously increase and decrease, leading to large polarizability derivatives. In turn, modes that provide relevant contributions to [μβ]0,0 are those in which oxygen anions move in opposite directions to the magnesium cations yielding large derivatives of the dipole moment and first hyperpolarizability.

Correction to “Analytic Density-Functional Theory Calculations of Pure Vibrational Hyperpolarizabilities: The First Dipole Hyperpolarizability of Retinal and Related Molecules”

Correction to “Analytic Density-Functional Theory Calculations of Pure Vibrational Hyperpolarizabilities: The First Dipole Hyperpolarizability of Retinal and Related Molecules”

Analytic Density Functional Theory Calculations of Pure Vibrational Hyperpolarizabilities: The First Dipole Hyperpolarizability of Retinal and Related Molecules

We present a general approach for the analytic calculation of pure vibrational contributions to the molecular (hyper)polarizabilities at the density functional level of theory. The analytic approach allows us to study large molecules, and we apply the new code to the study of the first dipole hyperpolarizabilities of retinal and related molecules. We investigate the importance of electron correlation as described by the B3LYP exchange-correlation functional on the pure vibrational and electronic hyperpolarizabilities and compare the computed hyperpolarizabilities with available experimental data. The effects of electron correlation on the pure vibrational corrections vary signficantly even between these structurally very similar molecules, making it difficult to estimate these effects without explicit calculations at the density functional theory level. As expected, the frequency-dependent first hyperpolarizability, which determines the experimentally observed second-harmonic generation, is dominated by the electronic term, whereas for the static hyperpolarizability, the vibrational contribution is equally important. As a consequence, frequency extrapolation of the measured optical hyperpolarizabilities can only provide an estimate for the electronic contribution to the static hyperpolarizability, not its total value. The relative values of the hyperpolarizabilities for different molecules, obtained from the calculations, are in reasonable agreement with experimental data.

Anharmonic IR and Raman spectra and electronic and vibrational (hyper)polarizabilities of barbituric, 2-thiobarbituric and 2-selenobarbituric acids

Infrared, Raman and electronic absorption spectra, electronic and vibrational (hyper)polarizabilities, of barbituric, 2-thiobarbituric and 2-selenobarbituric acids were studied in gas using ab initio and density functional theory levels. The vibrational spectra were computed using harmonic and anharmonic methods. Anharmonic contributions improve the agreement between calculated and available experimental wavenumbers, especially in the highest-energy spectral region (wavenumbers >1700cm−1). Vibrational and electronic transitions potentially useful to identify the investigated compounds were explored. The electronic and vibrational hyperpolarizabilities for the IDRI nonlinear optical (NLO) process at the λ value of 790nm were computed. Supported by spectroscopic results, electronic and vibrational polarizabilities and second-order hyperpolarizabilities increase progressively in the order barbituric acid<2-thiobarbituric acid<2-selenobarbituric acid. The seleno-derivative is predicted to be ca. three/four times more hyperpolarizable than the barbituric acid. The Se→O or Se→S substitutions can be practical strategies to enhances the NLO properties of barbituric and thiobarbituric acid-based materials.

On the vibrational linear and nonlinear optical properties of compounds involving noble gas atoms: HXeOXeH, HXeOXeF, and FXeOXeF

The vibrational (hyper)polarizabilities of some selected Xe derivatives are studied in the context of Bishop-Kirtman perturbation theory (BKPT) and numerical finite field methodology. It was found that for this set of rare gas compounds, the static vibrational properties are quite large, in comparison to the corresponding electronic ones, especially those of the second hyperpolarizability. This also holds for the dc-Pockels β(-ω;ω,0), Kerr γ(-ω;ω,0,0) and electric field second harmonic generation γ (-2ω;ω,ω,0) effects, although the computed nuclear relaxation (nr) vibrational contributions are smaller in magnitude than the static ones. HXeOXeH was used to study the effects of electron correlation, basis set, and geometry. Geometry effects were found to lead to noticeable changes of the vibrational and electronic second hyperpolarizability. A limited study of the effect of Xe insertion to the nr vibrational properties is also reported. Assessment of the results revealed that Xe insertion has a remarkable effect on the nr (hyper)polarizabilities. In terms of the BKPT, this is associated with a remarkable increase of the electrical and mechanical anharmonicity terms. The latter is consistent with the anharmonic character of several vibrational modes reported for rare gas compounds.

Solvation Effects on the Static and Dynamic First-Order Electronic and Vibrational Hyperpolarizabilities of Uracil: A Polarized Continuum Model Investigation

Electronic (β e) and vibrational (β v) first-order hyperpolarizabilities of uracil were determined in gas and water solution using the Coulomb-attenuating Density Functional Theory level with the Dunning's correlation-consistent aug-cc-pVDZ basis set. Frequency-dependent β e values were computed for the Second Harmonic Generation (SHG) and Electric Optical Pockels Effect (EOPE) nonlinear optical phenomena. The Polarized Continuum Model was employed to study the solvent effects on the electronic and vibrational properties. The introduction of solvation contributions increases the β e(static) value by ca. 110%. In comparison, smaller enhancements are found for the β e(EOPE) and β e(SHG) data evaluated at the typical wavelength of 694 nm (by 40–50%). The gas-water hyperpolarizability difference was rationalised through a density analysis study. The magnitudes of the vibrational first-order hyperpolarizabilities are comparable to their electronic counterparts and noticeably increase in solution: β v(EOPE) ~ β e(EOPE) in aqueous phase at λ = 694 nm. Analysis of the IR and Raman spectra is useful to elucidate the most important contributing modes to the vibrational first-order hyperpolarizabilities.

Electronic and Vibrational Nonlinear Optical Properties of Five Representative Electrides.

The electrides have a very special electronic structure with diffuse excess electrons not localized on any specific atom. Such systems are known to have huge electronic nonlinear optical (NLO) properties. Here, we determine and analyze the vibrational, as compared to the electronic, NLO properties for a representative set of electrides: Li@Calix, Na@Calix, Li@B10H14, Li2(•+)TCNQ(•-), and Na2(•+)TCNQ(•-). The static and dynamic vibrational (hyper)polarizabilities are computed by the nuclear relaxation method (with field-induced coordinates and the infinite optical frequency approximation) at the UB3LYP level using a hybrid Pople basis set. In general, the static vibrational βvec and γ∥ exceed the corresponding static electronic property values by up to an order of magnitude. The same comparison for dynamic vibrational hyperpolarizabilities shows a smaller ratio. For the intensity-dependent refractive index (IDRI) and dc-Kerr processes, the ratio is on the order of unity or somewhat larger; it is less for the dc-Pockels and the electric field induced second harmonic (EFISH) effects (as well as the static α̅) but still important. The role of anharmonicity, motion of the alkali atoms, and substitution of Na for Li is discussed along with specific aspects of the charge distribution associated with the excess electron.

Static and dynamic coupled perturbed Hartree-Fock vibrational (hyper)polarizabilities of polyacetylene calculated by the finite field nuclear relaxation method

The vibrational contribution to static and dynamic (hyper)polarizability tensors of polyacetylene are theoretically investigated. Calculations were carried out by the finite field nuclear relaxation (FF-NR) method for periodic systems, newly implemented in the CRYSTAL code, using the coupled perturbed Hartree-Fock scheme for the required electronic properties. The effect of the basis set is also explored, being particularly important for the non-periodic direction perpendicular to the polymer plane. Components requiring a finite (static) field in the longitudinal direction for evaluation by the FF-NR method were not evaluated. The extension to that case is currently being pursued. Whereas the effect on polarizabilities is relatively small, in most cases the vibrational hyperpolarizability tensor component is comparable to, or larger than the corresponding static electronic contribution.

Absolute Raman intensity measurements and determination of the vibrational second hyperpolarizability of adamantyl endcapped polyynes

Linear sp‐carbon polyynes are ideal molecules for the direct investigation of the physical properties of one‐dimensional conjugated systems. Traditionally, the main obstacle to the study of these systems has been their instability under normal laboratory conditions. Thanks to improved chemical syntheses, a broadened range of polyynes is now available for study, including the hydrocarbon series endcapped with adamantyl groups, Ad[n]. In this work, the quantitative Raman spectroscopic analysis is reported for each member of this homologous series. The Raman scattering intensities corresponding to the major features of the polyyne segment (i.e., the effective conjugation coordinate or Я lines) are then used to evaluate the nonlinear optical (NLO) behavior via determination of the vibrational contribution to the second hyperpolarizability (γvib). This study shows that γvib values as a function of length are of the same order of magnitude as those arising from the electronic contribution to the molecular second hyperpolarizability, γele, as reported for triisopropylsilyl polyynes, TIPS[n], using the differential optical Kerr effect technique. The nonlinear response for Ad[n] polyynes, supported by the analogous response for TIPS[n] polyynes, confirms that linear sp‐carbon molecules have large second hyperpolarizabilities that show a power‐law increase in γ‐values versus length that is larger than other known π‐conjugated systems, such as polyenes. Furthermore, the NLO response of polyynes versus length approaches the theoretical limit described by Kuzyk more closely than other conjugated organic oligomers. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Spectral Isolation and Measurement of Surface-Trapped State Multidimensional Nonlinear Susceptibility in Colloidal Quantum Dots

Multiresonant coherent multidimensional spectroscopy (CMDS) is a powerful new method for probing the coupling between vibrational modes and their dynamics. The line narrowing that occurs because of the multidimensional nature of CMDS allows the separation of homogeneous and inhomogeneous broadening and enhances spectral resolution. Recent work has extended multiresonant CMDS to electronic resonances in quantum confined nanostructures. Vibrational modes of the solvent also appear in the CMDS spectra. The phase oscillations of the vibrational and electronic coherences interfere and change the line shapes. Since the form of the vibrational third-order susceptibility and hyperpolarizability are well-known and since they can be measured against known standards, it becomes possible to use the interference effects as a probe of the absolute magnitude and phase of the electronic resonances. This approach is demonstrated using PbSe quantum dots where incomplete capping causes ultrafast relaxation to a new electron...