摘要:

31P chemical shielding and indirect dipolar coupling data of the polycrystalline fluorophosphates K2PO3F, Na2PO3F, BaPO3F and K2P2O5F2were obtained from broad-line and magic angle sample spinning31P N.M.R. measurements at 109·3 MHz. The N.M.R. spectra are interpreted in terms of the model established by Vander Hart and Gutowsky. For interpreting the spectrum of K2P2O5F2the theory was extended to the case of nonaxial31P chemical shielding tensors.

ISSN:0026-8976    

DOI:10.1080/00268978700100111

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The intermolecular potential energy function for the Ne-N2interaction has been studied. Newab initiocalculations of the short range energy have been carried out and these form the basis of the repulsive part of the potential. The long range potential uses published results for the dispersion energy coefficients and various types of damping function have been applied to the dispersion energy at medium and short separations. The best overall forms of potential have been assessed by critical comparisons with experimental results for the interaction second virial coefficients and the low pressure viscosity and diffusion coefficients.

ISSN:0026-8976    

DOI:10.1080/00268978700100121

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A model water-in-oil microemulsion is introduced in which the rigidity of the interfacial surfactant film is sufficiently large that it acts as the primary factor in determining the droplet structure of the disperse water phase. When the oil-water interface is saturated with surfactant, the excess surfactant unable to reside in the interfacial region is taken to form spherical micelles in the oil continuous phase and the microemulsion comprises a mixture of spherical marcroparticles. The small-angle scattering intensity is calculated as a function of the surfactant concentration for both X-ray and neutron scattering studies in both the dilute and concentrated regimes.

ISSN:0026-8976    

DOI:10.1080/00268978700100131

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Simulations of water models with and without intramolecular degrees of freedom have been performed within the classical approximation. Three H2O simulations with interaction parameters taken from a simple point charge model due to Berendsenet al.are reported: (i) with rigid water molecules, (ii) with flexible water molecules and (iii) with rigid water molecules and polarized bond lengths and bond angles obtained from the second simulation. The most important effect of the inclusion of intramolecular vibrations is seen on transport properties, which in general become a foctor of 2-3 faster. The internal vibrations lead to a small but significant lowering of the potential energy and also reduce the structure, as seen from atom-atom distribution functions. The dipole moment fluctuations are affected by the nuclear polarization caused by the intermolecular interactions. Two D2O simulation have been performed in order to assess the effects of isotope substitution, one with rigid molecules and the other with flexible.

ISSN:0026-8976    

DOI:10.1080/00268978700100141

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A technique is presented for the experimental determination and assignment of dipolar coupling constants from the N.M.R. spectra of molecules dissolved in liquid crystals. The technique is applicable to larger molecules than have been studied to date. Random deuteration of the molecule results in a statistical mixture of partially protonated species which can be analysed by two-dimensional and multiple quantum N.M.R. techniques to determine and assign all the dipole coupling constants. Benzene is used as an illustrative example.

ISSN:0026-8976    

DOI:10.1080/00268978700100151

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The cooperative dynamics in the high temperature disordered phase of tertiary butyl cyanide have been investigated using coherent inelastic neutron scattering techniques. Diffuse scattering peaks have been observed near Brillouin zone centres corresponding to Bragg reflections which are systematically absent in the disordered tetragonal phase but present in the low temperature ordered monoclinic phase and show clearly that local correlations exist which are closely similar in structure to that of the monoclinic phase. The extent of correlation of the local monoclinic structure within the disordered phase is approximately 2 unit cells and the correlation time for the cooperative relaxations among the four local structures is approximately 10-12s. The uniaxialC3molecular rotations present in both phases are strongly coupled with the fluctuations in the local structure and there is a suggestion that the two motions become decoupled on approaching the transition. Transverse and longitudinal acoustic phonons propagating in the [110] and [100] directions have been measured and the initial slopes to the dispersion curves are presented. A highly overdamped soft mode, assigned to the librational motion of the molecule, has been observed across the whole of the zone.

ISSN:0026-8976    

DOI:10.1080/00268978700100161

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A trivially modified version of Ladd's multipole expansion of dipolar lattice sums (equivalent to an Ewald sum) is tested in a series of computer simulations. For bulk dielectric properties the expansion converges very quickly, and the results are identical to reaction field calculations. Microscopic orientational correlations converge somewhat less quickly, but for a system of point dipoles the limiting structure is only marginally different from reaction field simulations with ϵRF= ∞.

ISSN:0026-8976    

DOI:10.1080/00268978700100171

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The absorption spectrum of CHF3in a free jet expansion has been recorded at a resolution of 0·004 cm-1in the 8–9 μm region. The line width is found to be essentially Doppler limited. An approximate rotational temperature of 40K has been determined from the spectrum. Relative intensities and transition moments for the interacting bands are discussed.

ISSN:0026-8976    

DOI:10.1080/00268978700100181

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Values of the second to the fifth virial coefficient are reported for the gaussian overlap model for hard molecules of spheroidal symmetry. Where possible, these results are compared with those for the corresponding hard ellipsoids. It is found that the two models give nearly identical results. It is suggested that the relative simplicity of the hard gaussian overlap model recommends it for future study.

ISSN:0026-8976    

DOI:10.1080/00268978700100191

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor