Calculated Dipole Moments Research Articles

Electronic structure of the SrH+ and BaH+ molecules with dipole moment and rovibrational calculations

The alkaline-earth metal hydrides and their corresponding ions are heteronuclear molecules that are essential in many fields especially in astrophysics and spectroscopy such as sunspots, stars, nebulae, the interstellar medium and chemical engineering. They are important systems in spectroscopy due to their visible bands which emerge in the absorption spectrum of sun. Due to the importance of hydride species and the lack of theoretical studies on some astronomical diatomic molecules is a main reason to investigate their electronic structure. The adiabatic potential energy curves and the static dipole moment curves of the low-lying electronic states of strontium hydride cation SrH+ and barium hydride cation BaH+ have been investigated using ab initio CASSCF/(MRCI + Q) calculations. The spectroscopic parameters Te, Re, ωe, Be, the dipole moment μe, and the dissociation energy De were calculated for the bound states. Using the canonical function approach, the rovibrational constants Ev, Bv, Dv and the turning points Rmin and Rmax for the ground and several excited states have been determined.

Cs3 Pb2 (CH3 COO)2 X5 (X=I, Br): Halides with Strong Second-Harmonic Generation Response Induced by Acetate Groups.

Nonlinear optical (NLO) crystals are the key component in solid-state lasers. New second-harmonic generation (SHG) effective halides, Cs3 Pb2 (CH3 COO)2 X5 (X=I, Br), have been rationally synthesized by introducing acetate groups into lead halide perovskites under moderate solvothermal conditions. Cs3 Pb2 (CH3 COO)2 X5 (X=I, Br) feature highly oriented anionic chains constructed by distorted [PbX4 O2 ] (X=I, Br) polyhedrons. Both the theoretical studies and the dipole moment calculations uncover that their SHG effects are mainly originated from the distorted [PbX4 O2 ] (X=I, Br) polyhedrons. Remarkably, Cs3 Pb2 (CH3 COO)2 I5 exhibits strong phase-matching SHG response (8×KDP) and large birefringence (0.26@ 1064 nm). Moreover, Cs3 Pb2 (CH3 COO)2 X5 (X=I, Br) also possess high laser damage threshold (LDT) which are almost 27 and 41 times that of AgGaS2 , respectively.

Cs3Pb2(CH3COO)2X5 (X=I, Br): Halides with Strong Second‐Harmonic Generation Response Induced by Acetate Groups

AbstractNonlinear optical (NLO) crystals are the key component in solid‐state lasers. New second‐harmonic generation (SHG) effective halides, Cs3Pb2(CH3COO)2X5 (X=I, Br), have been rationally synthesized by introducing acetate groups into lead halide perovskites under moderate solvothermal conditions. Cs3Pb2(CH3COO)2X5 (X=I, Br) feature highly oriented anionic chains constructed by distorted [PbX4O2] (X=I, Br) polyhedrons. Both the theoretical studies and the dipole moment calculations uncover that their SHG effects are mainly originated from the distorted [PbX4O2] (X=I, Br) polyhedrons. Remarkably, Cs3Pb2(CH3COO)2I5 exhibits strong phase‐matching SHG response (8×KDP) and large birefringence (0.26@ 1064 nm). Moreover, Cs3Pb2(CH3COO)2X5 (X=I, Br) also possess high laser damage threshold (LDT) which are almost 27 and 41 times that of AgGaS2, respectively.

Ground and excited state dipole moments of 1-methylindole from thermochromic shifts in absorption and emission spectra

The permanent dipole moments of 1-methylindole in its ground and lowest excited singlet ππ*-state have been determined using the method of thermochromic shifts of the absorption and fluorescence spectra and compared to ab initio calculated dipole moments. While ab initio theory predicts an excited state dipole moment, which nearly equals that of the ground state, the thermochromic shifts give an excited state dipole moment, which is about 2 Debye larger than that of the ground state. Perturbation of the excited state through the large electric field strength of the solvent cavity leads to strong mixing with the next excited singlet state, which has a considerably larger dipole moment. This perturbation is analyzed using the method described by Lombardi [John R. Lombardi J. Phys. Chem. A 1998, 102, 2817–2823]. The perturbing state could be identified as 1La-state, which is the second adiabatic state in the gas phase, but the lowest state in a polar surrounding.

A Nonlinear Optical Switchable Sulfate of Ultrawide Bandgap

Nonlinear optical (NLO) switchable materials have attracted intense attention because of their promising applications in optoelectronic devices. However, previous studies are mainly limited to mole...

Self-consistent electrostatic embedding for liquid phase polarization

While it is well known that molecules can be strongly polarized when transferred from the gas phase to a polar liquid, quantifying polarization effects explicitly using either experiment or theory has remained elusive. In this paper, we present a new QM/MM method involving a self-consistent calculation of the liquid state dipole moments, that is able to yield realistic, accurate estimates of the multipole moments of molecules in the liquid state. As a proof-of-concept, we apply our Self-Consistent Electrostatic Embedding (SCEE) method to the widely studied system of pure water. The method gives molecular dipole moments that are significantly enhanced with respect to the isolated gas-phase molecule and that are consistent with the best current experimental estimate of this property. While previous QM/MM calculations on the same system systematically underestimate the liquid dipole moment, those predictions become consistent with our own when several shortcomings are accounted for in an approximate way. Furthermore, sampling liquid configurations using several (but not all) fixed-charge force fields yields results that are consistent with sampling from a classical polarizable model. We then extract several contributions to the polarization energy (i.e. the change in energy when transferring a molecule from the gas to the liquid phase) and show that the distortion correction is cancelled out by the purely electronic contribution to the polarization energy. This insight is very important from the point of view of force-field development, since it allows us to unequivocally quantify the two missing energy terms in classical non-polarizable models. This provides a way to systematically improve predictions of phase-change energies (e.g. enthalpy of vaporization, hydration free energies) from such force-fields by correcting for the missing polarization effects.

Theoretical study of structural effects on reactivity and stability of isomeric pyrano-, thiopyrano-, and selenopyranopyrroles

In this study, global and local DFT reactivity descriptors for isomeric pyrano-, thiopyrano- and selenopyranopyrroles have been calculated. The geometric optimization of the obtained structures was realized with the density functional theory (DFT, B3LYP) at the level of 6-31G(d) and show these isomers have planar configurations. The structural properties such as dipole moments, bond lengths and bond angles of these isomers were calculated. The heats of formation have also been calculated based on the optimized geometry. The energies of HOMO and LUMO molecular orbitals are used to determine several global descriptors as a measure of their electronic properties, relative stabilities and chemical reactivities. These include total energy (E), ionization potential (I), electron affinity (A), chemical hardness (η), chemical softness (S), electronic chemical potentials (μ) and electrophilicity (ω). Selenopyrano[2,3-c]pyrrole possesses the highest electrophilicity and minimum chemical hardness among the calculated isomeric structures. The largest calculated dipole moment belongs to pyrano[3,2-b]pyrrole, while thiopyrano[3,4-b]pyrrole has the lowest.

Synthesis, Structure, and Characterization of d0 Transition-Metal Iodate: BaTi(IO3)6·0.5H2O.

A new noncentrosymmetric (NCS) d0 transition-metal (TM) iodate BaTi(IO3)6·0.5H2O has been successfully synthesized by the typical hydrothermal method. The single-crystal X-ray diffraction shows that BaTi(IO3)6·0.5H2O crystallizes in the polar trigonal space group R3 (no. 146) with a = b = 11.1920(12) Å, c = 24.006(3) Å. The reported compound features zero-dimensional (0D) [Ti(IO3)6]2- clusters that are separated by Ba2+ cations and bound water in the structure. By comparing BaTi(IO3)6·0.5H2O with the centrosymmetric (CS) α- and β-BaTi(IO3)6 that were reported before, it can be found that the bound water plays an important role for the formation of NCS structure for BaTi(IO3)6·0.5H2O. In addition, based on the powder second harmonic (SHG) measurement, BaTi(IO3)6·0.5H2O can achieve type-I phase matching with a moderate SHG effect (∼1 × KDP). The source of SHG effect was analyzed by dipole moment calculation and structure comparison. UV-vis-NIR diffuse reflectance spectroscopy, infrared spectroscopy, and thermogravimetric measurements are also presented.

Reappraisal of P, T-odd parameters from the improved calculation of electric dipole moment of 225Ra atom

By employing the recently developed relativistic normal coupled-cluster theory, we obtained the electric dipole moment (EDM) of 225Ra due to nuclear Schiff moment (NSM) and tensor–pseudotensor (T–PT) electron–nucleus (e–N) interaction as −6.3(5) × 10−17 S |e| cm/(|e| fm3) and −13(1) × 10−20 CT⟨σN⟩ |e| cm, respectively, for the NSM S, T–PT coupling coefficient CT and nuclear Pauli spinor σN. This is corroborated by analyzing the dipole polarizability value of 225Ra, which is obtained as 257(8) . Our EDM results, in combination with the measurement (2015 Phys. Rev. Lett. 114 233002), are about 8% and 28% improvements over the limits that were reported using the relativistic coupled-cluster theory for the NSM and T–PT e–N coupling coefficient, respectively. Further combining with the nuclear calculations, we infer limits on the EDM of neutron dn < 1.15 × 10−23 |e| cm, the EDM of proton dp < 1.1 × 10−22 |e| cm, the quantum chromodynamics parameter and the combined up- and down-quark chromo-EDMs . Though these bounds are not competitive at present with the current-best limits acquired from 199Hg atom, they can be bettered when the measurement of EDM in 225Ra improves by four orders.

Quantum mechanical calculations of dipole moment of diverse imines

Quantum mechanical calculations of dipole moment of diverse imines

Unique synthesis, structure determination, and optical properties of seven new layered rare earth tellurite nitrates, RE(TeO3)(NO3) (RE = La, Nd, Eu, Gd, Dy, Er, and Y)

Seven new rare earth tellurite nitrates, RE(TeO3)(NO3) (RE = La, Nd, Eu, Gd, Dy, Er, and Y), have been synthesized in closed autoclaves in the absence of solvent using TeO2 and corresponding rare earth metal nitrate hydrates. Although all the reported rare earth tellurite nitrates are stoichiometrically equivalent, the crystal structures are different. While RE1(TeO3) (NO3) (RE1 = La and Nd) crystallizing in the monoclinic space group, P21/n (No. 14) exhibit layered backbones composed of RE1O9, TeO3, and NO3 groups, RE2(TeO3)(NO3) (RE2 = Eu, Gd, Dy, Er, and Y), crystallizing in the orthorhombic space group, Cmca (No. 64) reveal layered frameworks consisting of RE2O8, TeO4, and NO3 units. The frameworks include infinite chains of (TeO3)n. Band gaps derived from the UV–vis diffuse reflectance spectral data for the title compounds range from 3.6 to 4.4 eV depending on the extent of 4d, 5d, and/or 4f orbitals of rare earth metal cations as well as the distortions arising from unsymmetrical tellurites. Other characterizations including infrared spectroscopy, thermal analyses, dipole moment calculations, and photoluminescence measurements are also discussed.

Unitary coupled cluster ground- and excited-state molecular properties.

A scheme for the calculation of molecular properties within the framework of unitary coupled-cluster (UCC) theory in both the electronic ground and excited states is presented. The scheme is based on an expectation-value ansatz, similar to the equation-of-motion coupled-cluster method or the intermediate state representation (ISR) approach of the algebraic-diagrammatic construction (ADC) scheme. Due to the UCC ansatz, the resulting equations cannot be given by closed-form expressions but need to be approximated. Explicit expressions for the expectation value of a general one-particle operator correct through second order in perturbation theory have been derived and coded for the electronic ground state as well as for excited states of predominant single-excitation character. The resulting equations are shown to be equivalent to those of the second-order ADC/ISR procedure. As first computational tests, the second-order UCC method (UCC2) and the one employing third-order amplitudes (also eigenvectors) together with the second-order density matrix, denoted as UCC3(2), are applied to the calculation of dipole moments for a series of small closed- and open-shell systems as well as 4-cyanoindole and 2,3-benzofuran and compared to full configuration interaction or experimental results. For the aromatic organic molecules, the UCC2 method is shown to be sufficient for the ground-state dipole moment, whereas the UCC3(2) scheme is superior for excited-state dipole moments.

N-Acetyl Indole Linked to a Fused Triazolo/Thiadiazole Scaffold: Synthesis, Single Crystal X-Ray Structure, and Molecular Insight

The designed target compound of N-acetyl indole linked to a fused triazolo/thiadiazole scaffold was synthesized via the reaction of 4-amino-5-(1H-indol-2-yl)-1,2,4-triazol-3(2H)-thione as the starting material with acetic anhydride under reflux conditions for 6 h, resulting in an excellent and pure chemical yield. The structural features of the designed compound were confirmed using spectroscopic tools including single crystal X-ray diffraction analysis along with 1H-NMR, 13C-NMR, 2D-NMR, and high resolution mass spectrometry. Using Hirshfeld analysis, we determined the molecular packing depends on strong interactions (O···H and N···H) along with weak interactions (S···H, C···H and H···H). The shortest contacts corresponding to the N3···H12 (2.490 Å), N2···H5 (2.503 Å), and O1···H2 (2.490 Å) interactions were confirmed based on the Hirshfeld analysis. The calculated dipole moment was 6.6557 Debye. The atomic charge distribution, molecular electrostatic potential map, and reactivity descriptors are also discussed. The computed NMR spectra of the requisite compound correlated well with the results obtained experimentally. The UV-Vis electronic spectra of the requisite compound were simulated using the TD-DFT method and compared with the experimental data. The different σ→σ*, π→π*, n→σ*, and n→π* donor–acceptor interactions and their interaction energies stabilized the studied system to 9.84, 20.65, 29.33, and 45.82 kcal/mol, respectively.

DFT calculation and experimental study on electronic structure and optical properties of 7-Amino-4-oxo-3-(2-(2-thienyl)vinyl)-4H,8H-[1,2,4]triazino[3,4-b][1,3,4]thiadiazine-8-carbonitrile thin films

Theoretical and experimental investigations of the structural and optical properties of 7-Amino-4-oxo-3-(2-(2-thienyl)vinyl)-4H,8H-[1,2,4]triazino[3,4-b][1,3,4]thiadiazine-8-carbonitrile thin films were carried out. The optimized geometrical parameters, the frequency of the vibrational bands, HOMO-LUMO energy gap, and total dipole moment calculations of the title compound were performed by the density functional theory (DFT) method at B3LYP/6-31 G(p,d) level of theory. Homogenous thin films of the title compound were successfully deposited on fused quartz substrates by thermal evaporation techniques. Spectrophotometer measurements were used to determine the optical parameters of the thin film in the wavelength range of 200−2500 nm. The dispersion parameters of the title compound thin films were illustrated in the light of single-oscillator model. The obtained values of the absorption coefficient and energy gap suggest that the title compound can be used in optoelectronic devices. The theoretical and experimental results were demonstrated good agreement.

Calculation of the Structure and Properties of Optical Nonlinear Fluorine-Containing Chromophores

Possible modifications of chromophore structures with nonlinear optical properties by bonding F atoms and F-containing groups to the acceptor site of the molecules are considered. Quantum chemical calculations of dipole moments and first hyperpolarizability were performed for several nonlinear chromophores based on N-ethyl- N-(2-hydroxyethyl)-4-phenylazoaniline and modified by the addition of F atoms and F-containing groups to the acceptor site. Positions of maxima in the electronic absorption spectrum and the Mulliken charges on the atoms are found. It is shown that addition of F atoms and F-containing groups to the chromophore acceptor site changes (increases) the efficiency parameter, defined as the product of the dipole moment and the first hyperpolarizability. The main parameters of a waveguide modulator made of an electro-optical polymer composite with F-containing chromophores embedded in it are estimated.

GSRB rotation and rovibration intensities for: The bent HOCl molecule, and for: Quantum monodromy in NCNCS

Considerable work has gone into identifying and delineating the effects of quantum monodromy on molecules. Recently this included consideration of transition intensities of the NCNCS molecule using ab initio electric dipole moment functions in the Generalised SemiRigid Bender (GSRB) model [M. Winnewisser et al. PCCP 16, 17373-17407 (2014)]. In that work a discrepancy between the observed and calculated spectra was discovered. The purpose of the present work is to identify the source of that discrepancy - is it due to the physics of monodromy itself or are other issues involved? To investigate this we use the same theoretical approach for the simpler molecule HOCl. This allows us to identify a programming error affecting the b-type rovibrational transitions. We show that the NCNCS spectrum calculated with the corrected GSRB model does reproduce the experimental spectrum for pure rotational transitions within the ν7 large amplitude bending vibrational states, starting from the ground state and progressing through levels at the monodromy energy and beyond, while also reproducing the a-type υ:1←0rovibrational spectrum. However, the discrepancy with regard to the b-type rovibrational transitions remains. We discuss possible reasons for this discrepancy. In the course of this work we obtain a good GSRB model for the bending vibration-rotation levels of the atmospherically important HOCl molecule and its isotopologues. With ab initio calculations of the electric dipole moment function the GSRB calculates the rotation and bending rovibrational spectrum of HOCl in agreement with other determinations and with experiment. Using the physically constrained GSRB model, errors in tabulated transitions (including in the HITRAN database) were easily identified.

Ab-initio study of the ground and low-lying excited states including the spin-orbit effect of RbBa molecule and laser cooling feasibility

In this work, we present a thorough theoretical structure and spectroscopic study of the ground and low lying excited states of RbBa molecule. High-level ab-initio calculations are performed, using MCSCF/MRCI+Q level of method, based on the effective core potential (ECP) and core-polarization potential (CPP) approach. The potential energy curves, spectroscopic parameters, vibrationnel energy levels of the 16(2,4Σ+,2,4Π,2,4Δ) first electronic states, with respect to the lowest five dissociation limits were calculated. The comparison of the spectroscopic constants of the ground state X2Σ+ with the available theoretical work, are in good agreement. The study of all the excited states is performed in this work for the first time. Afterwards, the spin-orbit operator is incorporated in valence MRCI calculation using optimized relativistic spin-orbit pseudo-potentials and 33 Ω states are generated and split into Λ-S states. In addition, both relativistic and non relativistic calculations of permanent and transition dipole moments are presented and discussed. Stimulated black body (T= 300 K) and spontaneous transition rates of vibrational states of X2Σ+ state were evaluated. The related vibrational lifetimes for RbBa are found to be in order of 103 s which is sufficiently large for ultracold experiments. Moreover, the vibrational life-time for the A2Σ+(v’) and A2П (v”) states are measured and the possibility of Laser Cooling for the RbBa molecule is discussed based on Franck–Condon factors calculation of A2Σ+ (v’)→ X2Σ+(v) and A2П(v”) → X2Σ+(v) transition. This work represents a significant contribution for experimentalists as it provides efficient information in order to form cold alkali and alkaline-earth RbBa molecules.

B12Y12 (Y: N, P) fullerene-like cages for exemestane-delivery; molecular modeling investigation

The present study aimed to assess the adsorption of Exemestane (Aromasin: AMS) drug on the boron nitride (B12N12) and boron phosphide (B12P12) fullerene-like cages in the solvent (water) and vacuum environments at the PBE/6-311 + G∗∗ and MPW1PW91/6-311 + G∗∗ theoretical levels. AMS drug can adsorbed on the B12N12 and B12P12 fullerene-like cages generally via their CO and C–H groups. The strong adsorption of AMS drug (state II) is observed through a carbonyl involves a σ bond and a π bond involving the 2p orbitals on the boron atoms of the B12N12 in the water environment compared to vacuum environment. Phosphorous substituted doping in the B12N12 has little influence on the adsorption of AMS for both environments. The electronic and structural features of the B12N12 in comparison with B12P12 can be enhanced when AMS drug adsorbed on it. The adsorption of the AMS to the B12N12 changes the polarity of the pure fullerene-like cage as displayed by the calculated dipole moment values. The calculated solvation energies reveal that the solubility of AMS interacting with B12N12 is enhanced to a greater extent compared with the pure one. B12N12 can thus function as a drug delivery carrier in the therapy of postmenopausal patients with advanced breast cancer.

Syntheses, characterization and calculations of LimAnM6O15 (A=Rb, Cs; M=Si, Ge; m+n=6)

Alike phosphates, silicates and germanates exclusively containing tetrahedral basic building units (BBUs) can also exhibit ultraviolet (UV) even deep-UV transitions. They are important for the design of new UV or deep-UV nonlinear optical (NLO) materials. In this paper, four new alkali metal silicates and germanates, Li2Rb4Si6O15, Li2Cs4Si6O15, Li3Rb3Ge6O15 and Li3Cs3Ge6O15 were successfully synthesized by a high temperature solid state reaction. They obey the general formula of LimAnM6O15 (A=Rb, Cs; M=Si, Ge; m+n=6) and all exhibit the Sr2Be2B2O7 (SBBO)-like structures. More importantly, Li3Rb3Ge6O15 and Li3Cs3Ge6O15 crystallize in the noncentrosymmetric (NCS) structures and exhibit remarkable phase-matched second harmonic generation (SHG) effect, 0.8×KH2PO4 (KDP) and 1×KDP, respectively. These indicate that they are potential as UV or deep-UV NLO materials. Furthermore, their optical and NLO properties as well as thermal properties were measured. The structure-property relationships were studied by the dipole moment calculations and the first-principles calculations.

Solvent polarity sensitive characteristics of various tautomers of azo compounds: Linear and nonlinear optical properties.

Solvents as complex environments can induce considerable effects on the physical, chemical and biological properties of solute molecules. In this work, solvent polarity sensitive characteristics of two tautomers of different azo compounds were studied by using of spectroscopic and Z-scan techniques. In this case, nature and various molecular interactions contribution on the spectral behaviors of azo and hydrazone forms of selected samples were investigated by Kamlet-Abboud-Taft and Catalan models. Moreover, the obtained results of Z-scan indicate that self-defocusing, saturable and reverse saturable absorption features of azo dyes depend highly on substituents and molecular environment polarity characteristic. In this case, media polarity properties have the same effects on the third order nonlinear absorption coefficient and nonlinear refractive index values. Therefore, by measuring one of the third order nonlinear optical coefficients, it is possible to predict solvent polarity effects on the other nonlinear optical coefficient. The calculated dipole moments with high values in the molecular excited state also reveal the probability of molecular charge transfer characteristics. In this case, by excitation process, sample I indicate high dipole moment values in comparison to other samples. Therefore, the results can give useful information about the application of selected samples for designing various optical devices.