摘要:

It is shown that the Widom method of evaluating the chemical potential of a fluid [6] which has been exploited recently to obtain liquid entropies and vapour pressures by computer simulation [5] can be used very simply and economically to predict the liquid-vapour coexistence line and the vapour pressure given the form of the potential. The method is illustrated explicitly for liquid chlorine and liquid bromine. It is quite general, is simpler to use than might have been anticipated and provides a powerful test of an assumed form of intermolecular potential.

ISSN:0026-8976    

DOI:10.1080/00268978000103101

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A series of one-electron properties, i.e. dipole, quadrupole, octupole moments, diamagnetic susceptibility, second moments and second moment anisotropies of charge distribution, electric field, electric field gradient, diamagnetic shielding, nuclear quadrupole coupling constant, have been obtained byab initioS.C.F. calculations for the molecules COF2, SO2F2and SOF2. The effect of the size of the gaussian basis sets, includingd-type polarization functions, as well as the contraction schemes on the latter properties have been studied for the COF2molecule. This study enables us to determine the basis giving the best results as compared to experiment. With this basis the calculations have been extended to the properties of the molecules SO2F2and SOF2. Good overall agreement with experiment is obtained.

ISSN:0026-8976    

DOI:10.1080/00268978000103111

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Molecular formulae for the isotropic and anisotropic scattering are derived by considering the internal field acting upon a molecule within a dense medium and its fluctuation caused by density fluctuations. The anisotropic scattering formula of classical theory is retained but modified by the factors of the internal field. The new formula for the isotropic scattering depends sensitively on the principal values of the optical polarizability tensor and on the parameters describing the anisotropic internal field. Assuming the internal field to be given by the semimacroscopic approach of the Onsager-Scholte model with an ellipsoidal cavity, comparison of the calculated isotropic Rayleigh factor with the experimental value allows a prediction of the degree of the cavity anisotropy for different liquid densities.

ISSN:0026-8976    

DOI:10.1080/00268978000103121

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Vibration-rotation energies of diatomic molecules are computed in a basis of cubic splines using a series expansion of the centrifugal potential instead of its fitting representation. The vibrational continuum wavefunctions can be evaluated in a mixed basis set, as the spline fitting technique previously used for the electronic potential makes the analytical integration of the new functions possible. The same fitting algorithm suggests a fast method for defining approximately the best locations of the knots to be used in the least squares spline representation of the potential.

ISSN:0026-8976    

DOI:10.1080/00268978000103131

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Orientational correlation functions derived from the rotational and rotovibrational Raman spectra of N2at 150 K and 585 amagat are compared with the results of a molecular dynamics simulation available in the literature. The angular momentum correlation function is also estimated from the experimental memory function and compared with the one obtained by simulation. Mean square torques, intermolecular correlations and interaction induced contributions are also discussed.

ISSN:0026-8976    

DOI:10.1080/00268978000103141

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

With the advent of accurate measurements on simple molecular systems, the usual electrostatic + polarization + exchange potential has been more and more subject to severe criticism. Owing to the universality of the sole analytical form actually at our disposal and to its reliability in interpreting the spectral response of hydracids trapped in low temperature rare gas matrices, we apply it to the determination of the geometry of molecular dimers HX-HX′, to the subsequent study of the low frequency coupled internal motions (the three coupled anharmonic librational modes describing the orientation of the internuclear axes and the intermolecular vibration mode) and to the calculation of the principal moments of inertia of the rotating complex. Although the calculated mean intermolecular distance appears 5 per cent shorter than the measured one, the close agreement between the internal zero point motion, averaged angular geometries and the beam experiment data clearly shows that such an analytical potential can accurately explain actual structural properties and low temperature dynamical properties of these complexes.

ISSN:0026-8976    

DOI:10.1080/00268978000103151

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The velocity autocorrelation functions and memory functions of dense classical fluids may be directly obtained from the static radial distribution functiong(r) in an approximate way. Following the Mori projection operator formalism, the memory functions may be related to the fluctuating force correlation. At low densities, these functions may be evaluated by following the trajectories of particle pairs in the interatomic potential. At higher densities, the force correlation functions can be evaluated approximately from particle pair trajectories via the potential of the mean force. The contributions to the memory function come mainly from particle pairs with rather specific and rather short interatomic distances. At higher temperatures, this specific distance is even shorter, hence the memory function decays quickly with time. At lower temperatures, a negative region of the memory function may develop. On the other hand, there is relatively little density dependence of the normalized memory function. The results for argon fluids at various densities and temperatures agree satisfactorily with the molecular dynamics and the Enskog values. The decrease of the diffusion coefficient with density is partly due to the nature ofg(r) which reflects the stronger clustering of atoms at higher densities.

ISSN:0026-8976    

DOI:10.1080/00268978000103161

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Proton spin lattice relaxation of pyridine-N-oxide-2,6-d2in dilute solution (0·2 M) with carbon tetrachloride has been measured at -12·6, 6·5, and 26·6°C. Using2H and14N decoupling, eight transitions were resolved and recovery was monitored after non-selective inversion. In absence of14N decoupling, scalar relaxation produced clearly visible effects on the proton recovery curves. Combined with measurements of deuterium relaxation of the 2,6-d2and 4-d derivatives, proton relaxation data (including effects of dipolar cross correlation) were used to determine all three rotational diffusion constants at each temperature. The in-plane spinning motion was found to be ∼four-fold more strongly dependent on viscosity than predicted by the slip rotational diffusion model, while motion about the other two principal axes proceeds at rates within ∼40 per cent of slip predictions.14N spin lattice relaxation data were combined with the anisotropic reorientation rates in efforts to determine liquid phase values of the14N quadrupole coupling parameters. A very small decrease from solid phase values provides the best overall fit to the relaxation data.

ISSN:0026-8976    

DOI:10.1080/00268978000103171

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The asymptotic convergence to constant terms of the Clebsch-Gordan coefficients is utilized to reduce the general non-axial, two dimensional like problem, into a one dimensional Toeplitz (up to 1/l) like problem. Then a compact expression for the spectrum is obtained which is valid for all the tumbling regime. The sensitivity of the lineshape expression to various reorientation processes is shown and discussed.

ISSN:0026-8976    

DOI:10.1080/00268978000103181

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A variation-perturbation method has been used to calculate the static dipole polarizabilities α∥and α⊥of the hydrogen molecule over the bond length range 0·6a0ˇ-Rˇ- 10·0a0. The unperturbed wavefunction consisted of an expansion of 80 terms and the first order perturbed wavefunction consisted of an expansion of 65 terms. These wavefunctions take explicit account of electron correlation. The results were averaged over the nuclear motion to give the polarizability and its anisotropy in a number of vibration-rotation states for the H2, HD and D2molecules. The work is a refinement of a well known calculation by Kołos and Wolniewicz. Non-adiabatic contributions to the results are estimated.

ISSN:0026-8976    

DOI:10.1080/00268978000103191

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor