摘要:

Multipole moments, up to and includingl= 6, and multipole polarizabilities up to and includingl+l′= 6, have been calculated, for the molecules dimethylether, methanol, methane and water, from LCAO-SCF wavefunctions using an AO basis set of DZ quality augmented with doubled-polarization functions at the non-hydrogen-, andp-polarization functions at the hydrogen atoms. The polarizabilities were obtained using Rayleigh-Schrödinger perturbation theory and the non-empirical Unsöld method. The long range isotropic coefficients,C6,C8, andC10have been calculated for all ten types of interactions between the four molecular species. For the interaction between like molecules an effectiveC6coefficient has been derived for comparison with experiment. The agreement between calculated values and experimental data, as far as available, is satisfactory.

ISSN:0026-8976    

DOI:10.1080/00268978600101641

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The conformational properties of flexible polymer chains in dilute and concentrated solutions have been studied by computer simulation using the molecular dynamics technique. The polymer itself is represented by a freely linked chain consisting of 16 beads and the low-molecular solvent by the same particles as the chain beads. Equilibrium properties of the chain such as the end-to-end distance, the radius of gyration and the average bond angle are computed. All these quantities are compared with those obtained for an isolated chain without solvent particles. We conclude that within the accuracy of our calculation the behaviour of the chain immersed in a monomeric solvent is mainly determined by intrachain interactions rather than by solvent effects, i.e. the solvent has almost no effect on the static structure of the chain. Studies of multiple chain systems at a density of 0·8 demonstrate that both the local chain conformation and chain dimensions are very similar to those expected for an ideal gaussian chain. The influence of attractive forces on the static properties is also investigated and a qualitative comparison of present results with those of other authors is made.

ISSN:0026-8976    

DOI:10.1080/00268978600101651

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A generalized theory for the correlation between the vibration and rotation of partially oriented molecules is developed, retaining the next terms beyond the leading ones in the Taylor series describing the functional dependencies of the internal and external potential energies of the molecules on their normal coordinates. This generalization is shown to be necessary for the cases where the orienting force is very weak due to cancellation of the forces acting on the different parts of the molecule. The theory is used together with the model of bond additivity of the anisotropic forces to reanalyse the dipolar couplings obtained from the N.M.R. spectra of methane and its deuterated analogues dissolved in liquid crystals. The results of the analysis point to the conclusion that the interaction of the methane molecule with its surroundings is dominated by the van der Waals forces acting on its atoms. The resulting information on this external force field provides qualitatively correct predictions about the order parameter of the hydrogen molecule, assuming that the H atoms in H2and CH4experience the same force field. The results also give support to the hypothesis that the orientation-dependent perturbations of the internal state of the molecule are generally dominated by the bond-bending deformations.

ISSN:0026-8976    

DOI:10.1080/00268978600101661

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Three moments of the collision induced absorption spectral density are computed with two- and three-body effects taken into account. A model free of adjustable parameters is applied to reproduce the density-dependent spectrum.

ISSN:0026-8976    

DOI:10.1080/00268978600101671

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Radiation-induced (dynamic) polarizations of electronic charge distributions on ligands may contribute to both the electric- and magnetic-dipole moments of 4f→ 4ftransitions in lanthanide complexes. These ligand-polarization effects on magnetic-dipole transition moments are examined in the present study, and their possible influence on the rotatory strengths of 4f→ 4ftransitions inchirallanthanide systems is given special attention. The ligand-polarization mechanism for magnetic-dipole transition moments is not likely to contribute significantly to the total dipole strengths of 4f→ 4ftransitions in noncentrosymmetric lanthanide systems. However, this mechanism may contribute significantly (or detectably) to the rotatory strengths of certain 4f→ 4ftransitions inchirallanthanide systems. The relative importance of these contributions will be greatest for transitions with predominantly |ΔJ| ≥ 2 character and with relatively largeUλ(λ = 2, 4, and 6) matrix elements.

ISSN:0026-8976    

DOI:10.1080/00268978600101681

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The dynamic susceptibilities of two dimensional and spherical top three dimensional rotor are calculated in the high-temperature approximation using the symmetry adapted functions as dynamical variables. The results are used to analyse dynamics for a simple system of asymmetric linear rotors coupled to the translational degrees of freedom.

ISSN:0026-8976    

DOI:10.1080/00268978600101691

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The125Te N.M.R. spectrum of tellurophene in three liquid crystals was recorded and analysed. The different orientational behaviour of tellurophene in the liquid crystals enabled the anisotropy of the tellurium-125 shielding tensor, σzz- 1/2(σxx+ σyy), and the difference σxx- σyyof the tensor elements to be determined. The resulting values are -1569 ± 21 ppm and 307 ± 26 ppm, respectively. The analysis of the125Te N.M.R. spectra is also discussed.

ISSN:0026-8976    

DOI:10.1080/00268978600101701

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The CoCl2-4ion has been studied usingab initiomethods at various levels of approximation (RHF, UHF, CI and MC SCF). The calculations have been performed both with and without the Madelung field from crystalline surroundings. One of the main purposes has been to investigate the spin density, and determine its dependence on both correlation and external fields. The spin density is found to be fairly dependent on correlation but rather independent of the surrounding crystal. The lower excited quartet states have been calculated using CI expansions based upon ground state RHF and MC SCF wavefunctions. The experimental spectrum is very well reproduced on the MC SCF/CI level, both with and without the Madelung field.

ISSN:0026-8976    

DOI:10.1080/00268978600101711

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Intramolecular motion in the biradical N,N'-bis(2,2,6,6-tetramethyl-1-oxyl-4-piperidinyl)ethylenediamine which contains two ionizable amine groups has been studied by E.S.R. spectroscopy. The line-shapes of the spectra as a function of pH and temperature were analysed by density matrix methods to give values for rates and free-energies of activation.

ISSN:0026-8976    

DOI:10.1080/00268978600101721

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A new method for evaluating free energy differences between thermodynamic states of a given system at different temperatures is proposed. The method is based on the study of the fluctuations of the mass scaling parametet that enters the newly developed canonical molecular dynamics method of Nosé [1]. The method is numerically tested in the calculation of the free energy of a 13-atoms Lennard-Jones cluster. In this case the method is computationally more effective then conventional methods and offers the possibility of checking the internal consistency of the results.

ISSN:0026-8976    

DOI:10.1080/00268978600101731

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor