Hartree—Fock—Slater functions as basis for one-electron perturbation calculations for molecules: I. Calculation of ground state electric dipole polarizabilities

The analysis of the decoupling of Hartree—Fock—Slater SCF perturbation equations for an external field is undertaken. The points of departure from the corresponding Hartree—Fock perturbation equations are stressed. Both formal and numerical results suggest that the fully uncoupled Hartree—Fock—Slater expression is a less drastic approximation than the same Hartree—Fock one. The uncoupled expression for the ground state electric dipole polarizability is calculated for CO, N₂, ethylene, acethylene and trans-butadiene in the dipole length—dipole length, dipole velocity—dipole length and dipole velocity—dipole velocity alternative formulations with an ab initio Hartree—Fock—Slater SCF basis set. The results compare well with other non-empirical results and the dipole velocity-dipole length results are in remarkably good agreement with experiments.     

The dispersion damping functions and interaction energy curves HeHe

Dispersion damping functions for the dipole—dipole, dipole—quadrupole, dipole—octupole, and quadrupole—quadrupole dispersion energy have been computed for HeHe. They are obtained using separated fragment polarizabilities of complex argument. The interaction energy is computed by adding the damped dispersion energy to the Hartree—Fock interaction energy. The resulting interaction energy curve is in excellent agreement with experiment.     

Second-order perturbation treatment of dipole—dipole scattering

Using second-order perturbation theory the contribution of the dipole—dipole potential to elastic scattering is calculated in the limit where the energy defect is large making the first-order terms negligible. The results do not agree with the Keesom—Linder potential commonly used to interpret data in this region.     

The rα-structure of thieno[2,3-b] thiophene. A 1H-NMR study in a nematic phase including 13C-satellites in natural abundance

The ¹H-NMR spectrum of thieno[2,3-b]thiophene in a nematic phase has been recorded and analysed. The ¹H,¹³C dipole—dipole couplings were obtained from ¹³C satellites in natural abundance. The indirect ¹H,¹H and ¹H,¹³C spin—spin coupling constants were determined from an isotropic sample. The dipole—dipole couplings were corrected for harmonic vibrational contribution. The corrected dipole—dipole couplings were used to evaluate the r_α-structure of the molecule.     

Differential cross sections from classical perturbation scattering theory. I. ion—dipole scattering

The formalism for calculating differential cross sections for atom—molecule scattering using classical perturbation scattering theory (CPST) is developed. The results are applied to the scattering of an ion by a dipolar molecule. The interaction potential used in the calculation consists of the ion—dipole and ion—induced dipole terms in the long-range expansion of the potential. Various approximate methods for calculating differential cross sections are also considered.     

A quantitative study of the effect of solvent on the electronic absorption and fluorescence spectra of substituted phenothiazines: evaluation of their ground and excited singlet-state dipole moments

Electronic absorption and fluorescence excitation and emission spectra of five phenothiazines (phenothiazine, promethazine, thionine, methylene blue and Azure A) were determined at room temperature (293 K) in several solvents of various polarities (cyclohexane, dioxane, ethyl ether, chloroform, ethyl acetate, 1-butanol, 2-propanol, ethanol, methanol, acetonitrile, dimethylformamide and dimethyl sulfoxide). The effect of the solvents upon the spectral characteristics was studied. In combination with the ground state dipole moments of these phenothiazines, the spectral data were used to evaluate their first excited singlet-state dipole moments by means of the solvatochromic shift method (Bakhshiev's and Kawski—Chamma—Viallet correlations). The theoretical ground and excited singlet-state dipole moments for phenothiazines were calculated as a vector sum of the π component (obtained by the Pariser—Parr—Pople method) and the σ component (obtained from σ-bond moments). A reasonable agreement was found with the experimental values. For most phenothiazines under study, excited singlet-state dipole moments were found to be significantly higher than their ground-state counterparts. The application of the Kamlet—Abboud—Taft solvatochromic parameters to the solvent effect on spectral properties of phenothiazines is discussed.     

Raman spectrum modification in the presence of solvated electrons. Observation by polarization CARS

The multiple-scattering series for depolarized light scattering from simple liquids is investigated. It is found that the leading term in the series, due to double—double scattering, is probably not large compared to double—triple (DT) scattering contributions. Existing theories, which neglect DT scattering, have concluded that the experimental data cannot be explained using the dipole—induced dipole (DID) model for the pair polarizability. It is suggested that a theory which includes DT scattering will not lead to rejection of the DID model.     

Spin—rotational relaxation study of molecular reorientation in the presence of internal extended rotational diffusion

Molecular reorientation in the presence of internal rotation is investigated and an analytical expression for the spin—rotational rate of a nucleus attached to the internal rotor is obtained in terms of the internal angular-momentum correlation time. A model of a symmetric-top molecule undergoing anisotropic rotational diffusion is extended to include a modified extended diffusion of internal rotation. The result is applied to liquid toluene and the internal angular-momentum correlation time is evaluated from the ¹³C nuclear spin—rotational relaxation rate of the methyl carbon. A comparison with the previous result on the dipole—dipole relaxation data is made and the consistency of the present theory is discussed.     

Multiferroic: A Polymer Composite Based on Organometallic Cobalt Dimers with Dzyaloshinskii–Moriya Effect

A magnetoelectric effect was discovered in polystyrene/organoelemental binuclear cobalt complexes with ligands of spatially hindered phenols at room temperature. The Dzyaloshinskii–Moriya interaction (dipole–dipole and anisotropic exchange interaction of unpaired electrons on cobalt ions at 77 K and room temperature) is fulfilled in such complexes. A novel class of high-temperature multiferroics—polymer composites—can be produced on the basis of such molecular structures.     

Spectroscopic investigation of magnetic dipole allowed transitions through the magnetic transition moment

An experimental technique for detecting magnetic dipole allowed transitions by their dispersion-induced circular dichroism (DICD) is discussed. The DICD spectra of three nitrogen heterocycles (pyridine, pyrazine and tetraphenylporphyrin) are shown to be dominated by the n — π^* transitions, as distinct from the normal absorption spectra which are dominated by the electric dipole allowed π — π^* bands.     

Rate coefficient for ion—dipole orbiting collisions

An improved version of the average dipole orientation (ADO) method is used to calculate the rate coefficient for ion—dipole orbiting (capture) rate coefficients. The results agree well with those obtained by the variational and by the statistical method.     

Dynamic polarizability of many-electron systems within a time-dependent density-functional theory

Using the time-dependent extension, proposed by us recently, of the Hohenberg—Kohn—Sham density-functional theory, in the presence of an oscillating electric field, we suggest a Karplus—Kolker-type variation—perturbation method for the calculation of dynamic 2^L-pole polarizability of many-electron systems. As an illustration of the present density-functional formalism, the frequency-dependent dipole polarizability of He atom has been calculated in the frequency range 0 ? ω ? 0.65 au, using local density forms of the exchange and correlation potentials. For ω = 0, the results are numerically better than recent density-functional calculations of the static dipole polarizability of He. The corresponding hydrodynamical formulation, which employs the single-particle density as a basic variable, is also presented.     

Critique of the mechanism of superselectivity in ion exchange membranes

One possible origin of permselectivity in situations where the Donnan equilibrium cannot exert much influence is investigated. The suggested origin of enhanced current efficiency beyond the Donnan limit is the existence of a coarse grained inhomogeneity in the distribution of “fixed” ions in the ion exchange membrane. Approximate solutions of the Nernst—Planck and Poisson equation for such inhomogeneous membranes are obtained for relevant highly idealized schematic situations in which only this single effect is investigated. Only “trends” are indicated, and the results do imply that “superselectivity” might be due to such inhomogeneity (possibly resulting from dipole clustering of fixed ionic groups), and that further, more precise, work should be carried out.     

Electric dipole polarity of diatomic molecules

The restricted SCF (single-configuration SCF) and MCSCF (multiconfiguration SCF) calculations are performed to compute the ground-state electric dipole moments of four pairs of diatomic molecules—(1) CO and BF; (2) SiO and AlF; (3) CS and BCl; and (4) SiS and AlCl—at a number of internuclear distances on both sides of the equilibrium position. Near Hartree–Fock accuracy is obtained in the SCF calculations. All eight molecules have a range of internuclear distance in which electric dipole moments are of the polarity of A^?B⁺. The shapes of computed electric dipole moment functions are discussed in the language of the molecular orbital method and in relationship to electronegativities of atoms. The present study gives us deeper understanding of electron transfer inside molecules and consequently of the apparent contradiction between electronegativity and the dipole polarity of some molecules. © John Wiley & Sons, Inc.     

Electron nuclear double resonance of 13C nuclei with natural abundance in trissarcosine calcium chloride doped with Mn2+ ions

¹³C ENDOR measurements were performed at 4.2 K on single crystals of trissarcosine calcium chloride doped with Mn²⁺ ions. Hyperfine coupling tensors were measured for six ¹³C nuclei of the carboxyl groups. An attempt is made to interpret the data in terms of electron-transfer and dipole—dipole contributions.     

A modification of the onsager theory for a dielectric

Onsager's theory of dipole moments is modified for radially inhomogeneous permittivity [form ?(r)=?_Bexp(—κ/r)] arising at the cavit Calculations show more consistent agreement between gaseous and liquid dipole moments with the modified theory.     

Molecular dipole polarizabilities based on MINDO/1 and MINDO/2 wavefunctions

Molecular dipole polarizability values are derived from a MINDO/1 — and MINDO/2 — “finite perturbation treatment”. The results are, especially in the MINDO/1 case, surprisingly good.     

Quantum theory of dielectric relaxation in polar solids

A novel approach to the impurity dipole relaxation in polar solids is described in which the dipole reorientational sites are formed by an appropriate electron—phonon coupling interaction. The electronic states used for a two-site formulation are defined as ones pertaining to the impurity and/or the associated intrinsic point defect. The theory takes into account the adiabaticity of the electron transfer in addition to the barrier-controlled ionic tunneling. It compares favorably with available experimental relaxation-time data on alkali halides.     

The role of electric interactions in the retention index concept; Implications in quantitative structure-retention studies

Summary A new equation is derived relating the retention index to the molecular polarizabilities, ionization potentials and permanent dipole moments of the stationary phase and the solute.Various implications of this equation to quantitative structure-retention relationships are discussed.