Calculation Of Polarizabilities Research Articles

Universal Scattering of Ultracold Atoms and Molecules in Optical Potentials

Universal collisions describe the reaction of molecules and atoms as dominated by long-range interparticle interactions. Here, we calculate the universal inelastic rate coefficients for a large group of ultracold polar molecules in their lower ro-vibrational states colliding with one of their constituent atoms. The rate coefficients are solely determined by values of the dispersion coefficient and reduced mass of the collisional system. We use the ab initio coupled-cluster linear response method to compute dynamic molecular polarizabilities and obtain the dispersion coefficients for some of the collisional partners and use values from the literature for others. Our polarizability calculations agree well with available experimental measurements. Comparison of our inelastic rate coefficients with results of numerically exact quantum-mechanical calculations leads us to conjecture that collisions with heavier atoms can be expected to be more universal.

Optical, vibrational (FT-IR and FT-Raman), electronic and molecular docking investigations of 1 Phenyl Isatin

In this work, FT-IR, FT-Raman and UV–vis spectra of 1 Phenyl Isatin (1PHISA) were carried out by using HF/6-31++G(d,p) and DFT/B3LYP method with 6-31++G(d,p),6-311++G(d,p) basis sets. The geometric parameters and wavenumbers were obtained and the complete assignments of fundamental vibrations were performed on the basis of potential energy distribution (PED) of the vibrational mode, calculated with scaled quantum mechanics (SQM) method. The hyper conjugative interaction leading to the stability of the molecule and delocalization of charge has been analyzed with natural bond analysis (NBO). HOMO-LUMO energy calculations show the charge transfer within the molecule. Molecular electrostatic potential, hyper polarizability calculations and thermodynamic functions of the compound were also calculated. The biological applications of 1PHISA have been screened out for antimicrobial activity such as antibacterial and antifungal activities. Molecular docking studies were also carried out for different receptors.

Benchmarking DFT approaches for the calculation of polarizability inputs for refractive index predictions in organic polymers.

In a previous study, we introduced a new computational protocol to accurately predict the index of refraction (RI) of organic polymers using a combination of first-principles and data modeling. This protocol is based on the Lorentz-Lorenz equation and involves the calculation of static polarizabilities and number densities of oligomer sequences, which are extrapolated to the polymer limit. We chose to compute the polarizabilities within the density functional theory (DFT) framework using the PBE0/def2-TZVP-D3 model chemistry. While this ad hoc choice proved remarkably successful, it is also relatively expensive from a computational perspective. It represents the bottleneck step in the overall RI modeling protocol, thus limiting its utility for virtual high-throughput screening studies, in which efficiency is essential. For polymers that exhibit late-onset extensivity, the employed linear extrapolation scheme can require demanding calculations on long-oligomer sequences, thus becoming another bottleneck. In the work presented here, we benchmark DFT model chemistries to identify approaches that optimize the balance between accuracy and efficiency for this application domain. We compare results for conjugated and non-conjugated polymers, augment our original extrapolation approach with a non-linear option, analyze how the polarizability errors propagate into the RI predictions, and offer guidance for method selection.

Optical and nonlinear optical properties of Ln(Tp)2, where Ln = La,…,Lu and Tp = tris(pyrazolyl)borate: a DFT+TD-DFT study

DFT calculations of electronic, structural, thermodynamic properties, magnetic moment, static and dynamic polarizability and hyperpolarizability of Ln(Tp)2 (Ln = rare earths, Tp = ring-unsubstituted tris(pyrazolyl)borate) complexes.

Chemical enhancement in the SERS spectra of indigo: DFT calculation of the Raman spectra of indigo-Ag14 complexes

The appearance of the Raman and the SERS spectra of indigo (IND) at 785 and 514 nm laser wavelength excitations has prompted the study of the interactions between the molecule and the silver substrate to which the molecule is adsorbed. In particular, no change of appearance between Raman and SERS spectra, apart some intensification, is observed at 785 nm excitation whereas some changes in the number and intensity of the bands are observed at 514 nm excitation. In a previous study a simplified model has been adopted where the molecule is simply bonded to an Ag2 cluster. Structural models have now been devised with the molecule is sited either perpendicular (edge-on) or planar (surface-on) to the surface of a Ag14 pyramidal cluster. The structure of the two complexes, the energy of the electronic excitations, the Raman spectra of the molecule/metal complexes have been studied through a TD-DFT simulation. The appearance of the experimental SERS spectra have been confronted with the prediction of the Herzberg–Teller surface selection rules of Lombardi et al., which have been formulated for the SERS spectra of molecules adsorbed on metal nanoparticles, in the frame of the Albrecht's theory for Raman scattering. The spectral predictions for the edge-on geometry fully meet the observation that the SERS spectra are dominated by totally symmetric Ag (under C2h symmetry) bands or, taking into account the lost of the inversion center after adsorption on the metal surface, in-plane A′ (under Cs symmetry) modes. This fully justifies the pop up of IR modes of the molecule in the SERS spectra, modes which belong to Bu and Au species in the free molecule C2h symmetry group. A systematic assignment of the modes of the free molecule and of the molecule in the complex has been made through the inspection of the calculated vibrational coordinates of the single vibrations. Dynamic polarizability (pre-resonance) calculations have been performed at 475 and 690 nm wavelength excitations, corresponding to the experimental 514 and 785 nm wavelengths, respectively. A small spectral enhancement is predicted at 690 nm for both complex geometries which should depend on charge transfer (CT) states calculated, albeit with very weak oscillator strength, in that spectral range. A substantial enhancement is instead calculated for both the edge-on and the surface-on models at the excitation wavelength of about 475 nm. The calculated Raman spectra intensification originates from the proximity of electronic excitations of intra-cluster, intra-molecular and CT type. The plasmonic excitation cannot be accounted for by the present model calculation. Natural Transition Orbitals (NTO) have been generated for the electronic excitations of both geometries, by transforming the ordinary orbital representation into a more compact form in which each excited state is expressed, if possible, as single pair of orbitals.

Structure, electrical and nonlinear optical properties of $$\hbox {M@C}_{20}$$ M@C 20 (M = Li, Na, K, Be, Mg and Ca) nanoclusters

The decoration of Li, Na, K, Be, Mg and Ca metal atoms on \(\hbox {C}_{20}\) fullerene was studied using the density functional theory (DFT) method. It was shown that the structure of the fullerene was intensely affected by the metal atom present. All metal atoms have exothermic adsorption on \(\hbox {C}_{20}\) fullerene, while Be has the highest value of adsorption energy, enthalpy and free energy. The presence of the metal atom also has a slight effect on \(E_\mathrm{g}\) while the lowest value of \(E_\mathrm{g}\) was obtained for \(\hbox {Ca@C}_{20}\). The calculations of polarizability and the first hyperpolarizability show that the metal atoms highly influence fullerenes. Among metal atoms, Ca atom had the highest effect and the other metal atoms led to an increase of the first hyperpolarizability to a value of approximately 42000 a.u. The time-dependent (TD)-DFT studies showed that \(\hbox {Ca@C}_{20}\) has the lowest excitation energies which is in agreement with the calculated first hyperpolarizability.

The influence of relativistic effects on nuclear magnetic resonance spin-spin coupling constant polarizabilities of H2 O2 , H2 S2 , H2 Se2 , and H2 Te2.

Relativistic and nonrelativistic calculations have been performed on hydrogen peroxide, dihydrogen disulfide, dihydrogen diselenide, and dihydrogen ditelluride, H2 X2 (X = O, S, Se, Te), to investigate the consequences of relativistic effects on their structures as well as their nuclear magnetic resonance (NMR) spin-spin coupling constants and spin-spin coupling constant polarizabilites. The study has been performed using both one-component nonrelativistic and four-component relativistic calculations at the density functional theory (DFT) level with the B3LYP exchange-correlation functional. The calculation of nuclear spin-spin coupling constant polarizabilities has been performed by evaluating the components of the third order tensor, nuclear spin-spin coupling polarizability, using quadratic response theory. From this, the pseudoscalar associated with this tensor has also been calculated. The results show that relativistic corrections become very important for H2 Se2 and H2 Te2 and hint that a new chiral discrimination technique via NMR spectroscopy might be possible for molecules containing elements like Se or Te. © 2018 Wiley Periodicals, Inc.

Generalized Gradient Approximation Exchange Energy Functional with Near-Best Semilocal Performance.

We develop and validate a nonempirical generalized gradient approximation (GGA) exchange (X) density functional that performs as well as the SCAN (strongly constrained and appropriately normed) meta-GGA on standard thermochemistry tests. Additionally, the new functional (NCAP, nearly correct asymptotic potential) yields Kohn-Sham eigenvalues that are useful approximations of the density functional theory (DFT) ionization potential theorem values by inclusion of a systematic derivative discontinuity shift of the X potential. NCAP also enables time-dependent DFT (TD-DFT) calculations of good-quality polarizabilities, hyper-polarizabilities, and one-Fermion excited states without modification (calculated or ad hoc) of the long-range behavior of the exchange potential or other patches. NCAP is constructed by reconsidering the imposition of the asymptotic correctness of the X potential (-1/ r) as a constraint. Inclusion of derivative discontinuity and approximate integer self-interaction correction treatments along with first-principles determination of the effective second-order gradient expansion coefficient yields a major advance over our earlier correct asymptotic potential functional [CAP; J. Chem. Phys. 2015 , 142 , 054105 ]. The new functional reduces a spurious bump in the CAP atomic exchange potential and moves it to distances irrelevantly far from the nucleus (outside the tail of essentially all practical basis functions). It therefore has nearly correct atomic exchange-potential behavior out to rather large finite distances r from the nucleus but eventually goes as - c/ r with an estimated value for the constant c of around 0.3, so as to achieve other important properties of exact DFT exchange within the restrictions of the GGA form. We illustrate the results with the Ne atom optimized effective potentials and with standard molecular benchmark test data sets for thermochemical, structural, and response properties.

A systematic study of the effects of thionation in naphthalene dimide derivatives to tune their nonlinear optical properties

In the present study, the number and position of sulfur atoms on naphthalene diimide (NDI) is systematically investigated to tune its nonlinear optical (NLO) response properties. Our DFT calculations for third-order polarizability (γ) show that the thionation significantly influences the nonlinear optical property of NDI as it is seen among its several designed derivatives (NDI-1 to NDI-10). The smallest and the largest γzzzz amplitudes are 503.49 × 10−36 and 1299.5 × 10−36 esu for NDI-1 (having tetraone group) and NDI-10 (having tetrathione group), respectively. The increase in γzzzz amplitude for NDI-10 is 796 × 10−36 esu, which is ∼150% from the γzzzz amplitude of NDI-1. A comparison of the γzzzz amplitudes of our designed derivatives are made with para-nitroaniline i.e. a prototype NLO molecule. The γzzzz amplitude of pNA is found to be 42.64 × 10−36 esu at the same B3LYP/DZVP2 level of theory. Using two-level model, the origin of larger γzzzz amplitudes is traced in lower transition energy of NDI-10. Furthermore, the calculation of vertical ionization potentials (VIPs) shows that the thionation does not affect the stability of designed derivatives, where a slight difference of 0.06 eV is seen between the VIPs of NDI-1 (6.63 eV) and NDI-10 (6.57 eV). Thus, a systematic comparison of the third-order polarizability and other electro-optical properties of our designed derivatives shows that our derivative systems possess good potential for their practical realization in the field of optical and NLO materials.

How Pb2+ Binds and Modulates Properties of Ca2+-Signaling Proteins

Abiogenic lead (Pb2+), present in the environment in elevated levels due to human activities, has detrimental effects on human health. Metal-binding sites in proteins have been identified as primary targets for lead substitution resulting in malfunction of the host protein. Although Pb2+ is known to be a potent competitor of Ca2+ in protein binding sites, why/how Pb2+ can compete with Ca2+ in proteins remains unclear, raising multiple outstanding questions, including the following: (1) What are the physicochemical factors governing the competition between Pb2+ and Ca2+? (2) Which Ca2+-binding sites in terms of the structure, composition, overall charge, flexibility, and solvent exposure are the most likely targets for Pb2+ attack? Using density functional theory combined with polarizable continuum model calculations, we address these questions by studying the thermodynamic outcome of the competition between Pb2+ and Ca2+ in various model Ca2+-binding sites, including those modeling voltage-gated calcium channel selectivity filters and EF-hand and non-EF-hand Ca2+-binding sites. The results, which are in good agreement with experiment, reveal that the metal site's flexibility and number of amino acid ligands dictate the outcome of the competition between Pb2+ and Ca2+: If the Ca2+-binding site is relatively rigid and crowded with protein ligands, then Pb2+, upon binding, preserves the native metal-binding site geometry and at low concentrations, can act as an activator of the host protein. If the Ca2+-binding site is flexible and consists of only a few protein ligands, then Pb2+ can displace Ca2+ and deform the native metal-binding site geometry, resulting in protein malfunction.

Time Domain Simulations of Single Molecule Raman Scattering.

Nonequilibrium chemical phenomena are known to play an important role in single molecule microscopy and spectroscopy. Herein, we explore these effects through ab initio molecular dynamics (AIMD)-based Raman spectral simulations. We target an isolated aromatic thiol (thiobenzonitrile, TBN) as a prototypical molecular system. We first show that the essential features contained in the ensemble-averaged Raman spectrum of TBN can be reproduced by averaging over 18 short AIMD trajectories spanning a total simulation time of ∼60 ps. This involved more than 90 000 polarizability calculations at the B3LYP/def2-TZVP level of theory. We then illustrate that the short trajectories (∼3.3 ps total simulation time), where the accessible phase space is not fully sampled, provide a starting point for understanding key features that are often observed in measurements targeting single molecules. Our results suggest that a complete understanding of single molecule Raman scattering needs to account for molecular conformational flexibility and nonequilibrium chemical phenomena in addition to local optical fields and modified selection rules. The former effects are well-captured using the described AIMD-based single molecule Raman spectral simulations.

Tuning of optical properties of p-phenyl ethenyl-E-furans: A Solvatochromism and Density functional theory.

p-Phenyl ethenyl-E-furans (1-6) with varied electron donor and acceptor substituent (NO2, CN, Cl, H, OCH3, NH2) were synthesized and studied the substituent induced optical properties (dipole moment, transition dipole moment, oscillator strength, optical band gap, hyperpolarizability) using Solvatochromism and Density functional theory. It is shown that furan acts as a weak electron donor in presence of an electron withdrawing p‑phenyl substituent (NO2, CN, Cl), whereas furan acts as a weak electron acceptor in presence of an electron donating p‑phenyl substituent (OCH3, NH2). In comparison to ethenylfuran 4, the HOMO-LUMO energy band gap is decreased upon increasing the electron donating or electron withdrawing nature of the phenyl ring. Calculation of excited state dipole moment and polarizability of 1-6 in solvent of varying polarity suggest that the nitro and amino compounds (1, 6) exhibit charge transfer excited state, whereas excited state of compounds 3-5 is non-polar in nature. As compared to the ethenylfuran (4), the first hyperpolarizability (β) is increased in presence of a strong electron withdrawing or strong electron donating p‑phenyl substituent. The higher β value is found for ethenylfuran with p‑nitrophenyl and p‑amino phenyl substitution. Overall, these studies provide useful information in tuning the optical properties of p‑phenyl substituted heterocyclic ethenyl systems.

Precision spectroscopy of helium in a magic wavelength optical dipole trap

Improvements in both theory and frequency metrology of few-electron systems such as hydrogen and helium have enabled increasingly sensitive tests of quantum electrodynamics (QED), as well as ever more accurate determinations of fundamental constants and the size of the nucleus. At the same time advances in cooling and trapping of neutral atoms have revolutionized the development of increasingly accurate atomic clocks. Here, we combine these fields to reach the highest precision on an optical tranistion in the helium atom to date by employing a Bose-Einstein condensate confined in a magic wavelength optical dipole trap. The measured transition accurately connects the ortho- and parastates of helium and constitutes a stringent test of QED theory. In addition we test polarizability calculations and ultracold scattering properties of the helium atom. Finally, our measurement probes the size of the nucleus at a level exceeding the projected accuracy of muonic helium measurements currently being performed in the context of the proton radius puzzle.

Dipole polarizability calculation of the Cd atom: Inconsistency with experiment

Three earlier relativistic coupled-cluster (RCC) calculations of dipole polarizability ($\alpha_d$) of the Cd atom are not in good agreement with the available experimental value of $49.65(1.65) \ e a_0^3$. Among these two are finite-field approaches in which the relativistic effects have been included approximately, while the other calculation uses a four component perturbed RCC method. However, another work adopting an approach similar to the latter perturbed RCC method gives a result very close to that of experiment. The major difference between these two perturbed RCC approaches lies in their implementation. To resolve this ambiguity, we have developed and employed the relativistic normal coupled-cluster (RNCC) theory to evaluate the $\alpha_d$ value of Cd. The distinct features of the RNCC method are that the expression for the expectation value in this approach terminates naturally and that it satisfies the Hellmann-Feynman theorem. In addition, we determine this quantity in the finite-field approach in the framework of A four-component relativistic coupled-cluster theory. Considering the results from both these approaches, we arrive at a reliable value of $\alpha_d=46.02(50) \ e a_0^3$. We also demonstrate that the contribution from the triples excitations in this atom is significant.

Additive polarizabilities of halides in ionic liquids and organic solvents.

The design of room-temperature ionic liquids featuring high refractive indices is desirable for a number of applications. Introducing strongly polarizable (poly)halides as anions is a promising route to increase the polarizability of an ionic liquid and thus the refractive index. Based on the experimental refractive indices and mass densities of imidazolium ionic liquids, additive atomic polarizabilities and volumes for chlorine, bromine, and iodine are determined. In addition, atomic polarizabilities and volumes for halide atoms in organic solvents are calculated and compared to ionic liquids. We find that especially iodine behaves differently in anions than in neutral or cationic species. A quantum-mechanical calculation of molecular and atomic polarizabilities complements and enhances the designed regression analysis. The gained insights into halide polarizability and volume are deployed to predict the refractive index of arbitrary ionic liquids.

Structural, Electronic and Nonlinear Optical Properties of Novel Derivatives of 9,12-Diiodo-1,2-dicarba-closo-dodecaborane: Density Functional Theory Approach

Abstract Using density functional theory (DFT) methods, we shed light on the structural, optical, electronic, and nonlinear optical (NLO) properties of three derivatives of 9,12-diiodo-1,2-dicarba-closo-dodecaborane(12) (C2H10B10I2). The DFT and time-dependent DFT methods are considered very precise and practical to optimize the ground and excited state geometries, respectively. A vibrant intramolecular charge transfer from highest occupied molecular orbitals (HOMOs) to the lowest unoccupied molecular orbitals (LUMOs) was observed in all compounds. The geometrical parameters of the experimental crystal structure, i.e. bond lengths/angles, have been successfully reproduced. The HOMO and LUMO energies, as well as their energy gaps (E g), were also calculated and compared with each other for all derivatives. The effect of attached groups on electronic, optical, and NLO properties along with detailed structure-property relationship was discussed. For NLO response, the CAM-B3LYP functional along with relatively larger basis set 6-31+G** (for hydrogen, carbon, boron, and oxygen atoms) and LANL2DZ (for iodine atoms) have been used to optimize the compounds at ground states. The calculation of second-order NLO polarizabilities (β tot) shows that compounds 2 and 3 possess the β tot amplitudes of 3029 and 4069 a.u., respectively, with CAM-B3LYP method that are reasonably larger than similar prototype molecules. Owing to their unique V-shapes, the nonlinear anisotropy values are found to be 0.63, 0.34, and 0.44 for compounds 1–3, respectively, which show the significant two-dimensional character of these compounds. Thus, the NLO amplitudes as well as the nonlinear anisotropies indicate that the above-entitled compounds are good contenders for optical and NLO applications.

Electric dipole polarizability ofXe129using the relativistic coupled-cluster and the normal coupled-cluster methods

$^{129}$Xe is an important candidate for the searches of electric dipole moments due to violations of time-reversal and parity violations in diamagnetic atoms. In view of the similarities between the electric dipole moment and the polarizability from the point of view of many-body theory, we have performed rigorous calculations of the ground state polarizability of $^{129}$Xe using a self consistent relativistic coupled-cluster method and the relativistic normal coupled-cluster method. The discrepancy between the results from these two methods is two percent, but each of them differs from the accurate measurement of the polarizability of the ground state of $^{129}$Xe by one percent. Our results clearly suggest that the two theoretical methods, we have employed in this work, can be applied in the future to capture electron correlation effects in the electric dipole moment of $^{129}$Xe to a high degree of accuracy.

Structure, stability, catalytic activity, and polarizabilities of small iridium clusters**Project supported by the CNPq, CAPES, and FAPES (Brazilian Agencies).

At the second order Douglas–Kroll–Hess (DKH2) level, the B3PW91 functional in conjunction with the relativistic all-electron basis set of valence triple zeta quality plus polarization functions are employed to compute bond lengths, dissociation energies, vertical ionization potentials, and the highest occupied molecular orbital-lowest unoccupied molecular orbital energy gaps of the small iridium clusters (Irn, n ⩽ 8). These results are compared with the experimental and theoretical data available in the literature. Our results confirm the theoretical predictions made by Feng et al. about the catalytic activities of the Ir4 and Ir6 clusters. From the optimized geometries, DKH2 calculations of static electric mean dipole polarizabilities and polarizability anisotropies are also carried out. It is the first time that the polarizabilities of small iridium clusters have been studied. For n ⩽ 4, the mean dipole polarizabilities per atom present an odd–even oscillatory behavior, whereas from Ir5 to Ir8, they decrease with the cluster size increasing. The dependence of the polarizability anisotropy on the structure symmetry of the iridium cluster is verified.

Spectroscopic and DFT approach for structure property relationship of red emitting rhodamine analogues: A study of linear and nonlinear optical properties

Abstract Linear and nonlinear optical (NLO) properties of triphenyl fused rhodamine analogues were estimated by spectroscopic based mathematical calculations and compared with computed values using density functional theory (DFT) calculations. Various Global hybrids (GHs) and range separated hybrids (RSHs) were utilized for reliable estimations of NLO properties. Spectroscopic based mathematical calculations of polarizability (αCT), first order hyperpolarizability (βCT) and second order hyperpolarizability (γ) were performed in varying polarity solvents. Spectroscopic based mathematical calculted αCT, βCT and γ values are found to have much closer agreement with the DFT computed values obtained by using RSHs. Comparative analysis of αCT, βCT and γ values suggested that these values increases with the increase of triphenylamine substitutions. Moreover, αCT, βCT and γ values increase with decreasing HOMO-LUMO band gap for all the dyes. N-[9-(isobenzofuran-1(3H)-one)-6-(dipnenylamino)-xanthene]-N-diphenyl amine having bis-triphenylamine substituent showed the largest NLO response among all analogues dyes.

High-precision measurements and theoretical calculations of indium excited-state polarizabilities

We report measurements of the $^{115}$In $7p_{1/2}$ and $7p_{3/2}$ scalar and tensor polarizabilities using two-step diode laser spectroscopy in an atomic beam. The scalar polarizabilities are one to two orders of magnitude larger than for lower lying indium states due to the close proximity of the $7p$ and $6d$ states. For the scalar polarizabilities, we find values (in atomic units) of $1.811(4) \times 10^5$ $a_0^3$ and $2.876(6) \times 10^5$ $a_0^3$ for the $7p_{1/2}$ and $7p_{3/2}$ states respectively. We estimate the smaller tensor polarizability component of the $7p_{3/2}$ state to be $-1.43(18) \times 10^4$ $a_0^3$. These measurements represent the first high-precision benchmarks of transition properties of such high excited states of trivalent atomic systems. We also present new ab initio calculations of these quantities and other In polarizabilities using two high-precision relativistic methods to make a global comparison of the accuracies of the two approaches. The precision of the experiment is sufficient to differentiate between the two theoretical methods as well as to allow precise determination of the indium $7p-6d$ matrix elements. The results obtained in this work are applicable to other heavier and more complicated systems, and provide much needed guidance for the development of even more precise theoretical approaches.