摘要:

Molecular dynamics simulations of liquid dichloromethane CH2Cl2and chloroform CHCl3have been carried out at two different temperatures. The calculations are based on new pair potentials derived in part fromab initiodata. The results on thermodynamics, static structure, self diffusion coefficients and the rotational motion are compared with experimental and other molecular dynamics results.

ISSN:0026-8976    

DOI:10.1080/00268978500100991

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Inspired by the experimental work of Richteret al.[1], we have investigated the dynamic behaviour of pairs of particles of a Lennard-Jones liquid for four different thermodynamic states. The short and long time behaviour of dynamic correlation functions of pairs are studied and directly compared with that of single particle correlation functions. Only those relating to singlet and pair diffusion are treated.

ISSN:0026-8976    

DOI:10.1080/00268978500101001

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Five absorption bands of the allowed 5d←4ftransitions of Ce3+were detected in the ultraviolet region between 37 and 51 × 103cm-1by σ- and π-polarized absorption, luminescence excitation, and MCD spectra with the single crystals of Ce3+doped lanthanum ethylsulphate enneahydrate. In the crystal, Ce3+is in aD3hligand field of nine water molecules such as in [Ce(OH2)9]3+.

ISSN:0026-8976    

DOI:10.1080/00268978500101011

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The dispersion relations for surface waves on a planar liquid surface are obtained from first principles. The high-frequency elastic, low-frequency hydrodynamic and intermediate viscoelastic regimes are investigated separately. It is shown that the structure of the liquid surface modifies the expression for Rayleigh's elastic surface waves and Kelvin's capillary waves and allows for the existence of new surface waves besides those of the phenomenological theories. For example, an hydrodynamic counterpart to the Rayleigh waves and an elastic counterpart to the capillary waves are found. The experimental observation of these surface waves could in principle yield direct access to the structure of the liquid surface.

ISSN:0026-8976    

DOI:10.1080/00268978500101021

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

By employing an anisotropic scaling of the cartesian coordinates, the properties of a system of perfectly aligned ellipsoidal molecules can be exactly related to the analogous properties of a system of spherical molecules. This approach is used to determine for such a model system the structure of the liquid surface and the orientational dependence of the surface tension. It is found that the surface tension and surface stiffness are no longer equal as they are in an isotropic liquid. The smectic phase is absent, while a continuum of crystal phases exist, differing in the relative orientation between the molecular axis and the crystal axis.

ISSN:0026-8976    

DOI:10.1080/00268978500101031

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

This paper reports a molecular dynamics study of the structure of water around Li+, Na+, K+, Ca++, Ni++and Cl-ions. Jorgensen's TIP4P potential is used for the water-water interaction, and newab initioSCF potentials have been obtained for Ca++/H2O and Ni++/H2O using the recently developed gradient method. In most cases where experimental results are available the positions of the peaks associated with the coordination shells, the ion-water geometries, and the coordination numbers are in satisfactory agreement. However, we believe that more precise neutron measurements of the coordination number of Ni++in dilute solution are needed. The main effects of high pressure on the structure of water around Cl-occur in the second coordination shell. High temperature and high pressure are found to have little effect on the structure around Ca++.

ISSN:0026-8976    

DOI:10.1080/00268978500101041

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Density-density correlations in a planar interface of a neutral, multi-component fluid mixture are analysed. For a ‘normal’ liquid-gas or liquid-liquid interface the transverse (parallel to the interface) correlations exhibit Ornstein-Zernike behaviour with a common correlation length ξT= (σ/b)1/2, where σ is the surface tension andbis determined by the external fields. If, however, the interface corresponds to a near complete wetting situation so that a thick film of a third fluid phase (β) intrudes between the two bulk phases α and γ, the transverse correlations do not, in general, exhibit Ornstein-Zernike behaviour. Rather they exhibit more complex structure for small transverse wave numbers which depends on the ‘stiffness’ of the wetting film. In the limit of a very thick film Ornstein-Zernike behaviour occurs in both edges, the correlation length depending on the value of σ andbappropriate to the individual interface so that ξαβT= (σαβ/bαβ)1/2and ξβγT= (σβγ/bβγ)1/2. The theoretical analysis is supported by the results of density functional calculations for a model binary fluid mixture, the parameters of which are chosen to mimic the experimentally observed situation in which the liquid phase (β) with the larger mass density forms a wetting film that intrudes between the less dense liquid phase (γ) and the gas (α). The resulting transverse correlation functions depend sensitively on the thickness of the film. Possible destabilization mechanisms for wetting films in gravitational fields are mentioned.

ISSN:0026-8976    

DOI:10.1080/00268978500101051

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The Raman spectra of the symmetric stretchingv1(A′1) mode of NO3-ions have been measured in a series of molten nitrates, LiNO3, NaNO3, KNO3, RbNO3, CsNO3, AgNO3, TlNO3, at a temperature 10–20 K above each melting point. Temperature dependence of the Raman spectrum was also measured in molten NaNO3. Reorientation of the symmetry axis of an nitrate ion is represented by the inertial motion of an associated ion cluster for short times and by rotational diffusion for longer times. One observes a point of inflection between two types of rotational motion at 0·2–0·5 ps. The speeds of inertial rotation and rotational diffusion decrease in the order, CsNO3, RbNO3, KNO3, NaNO3, TlNO3, LiNO3, AgNO3. The ratio of the effective moment of inertia obtained from moment analysis to the theoretical moment of inertia for a free NO3-ion,I/I0, increases in the same order, from 2·0 for CsNO3to 20 for AgNO3.

ISSN:0026-8976    

DOI:10.1080/00268978500101061

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A molecular orbital perturbation approach has been developed to explain the varying Overhauser enhancements observed for chemically shifted nuclei within a solvent molecule. Assuming that these chemically inequivalent nuclei have the same dipolar interaction with the unpaired electron on the free radical solute, the differential enhancements can be ascribed to varying scalar interaction. This methodology allows the estimation of the induced spin density at a particular nucleusN, in the solvent molecule due to the nucleus—unpaired electron scalar interaction. The solvent molecule is considered as a closed-shell system in the CNDO/INDO framework, and the free radical is modelled by a single 2p-orbital of the pi-type centred on the oxygen atom. The Coulomb interaction between the unpaired electron on the free radical and those in the solvent molecule is considered as a perturbation. As a test of the theory we report our results for the induced spin density at the19F nuclei for the system 1,2,4-trifluorobenzene and tri-tertiary butyl phenoxyl. The theoretically predicted ordering parallels the experimental observations. We have also evaluated the scalar coupling constant for the system hexafluorobenzene—tri-tertiary butyl phenoxyl. The theoretical result is in satisfactory agreement with experimental data.

ISSN:0026-8976    

DOI:10.1080/00268978500101071

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The simplest form of Herzberg-Teller theory involves the vibronic coupling of a single mode between two energetically separated molecular states. An adiabatic analysis of this system is presented which incorporates the effect of the distant state without recourse to direct summation over distant energy levels. The theory is compared to exact numerical results for vibronic-coupling in propynal and formaldehyde. The adiabatic eigenvalues are exceptionally accurate, especially if proper radial Born-Oppenheimer terms are added to the adiabatic potential for the ground state. The quality of the resultant amplitudes associated with the distant state are adequate to represent any intensity borrowing effects in the molecular spectra to well within 5 per cent. The adiabatic theory is quite general and can be used with equal force to represent distant perturbations due to repulsive as well as attractive states, and without any commitment to linear vibronic coupling models.

ISSN:0026-8976    

DOI:10.1080/00268978500101081

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor