摘要:

We investigate the statistical-mechanical basis and the numerical accuracy of the Smoluchowski-Poisson-Boltzmann (SPB) approximation for describing ion diffusion in non-uniform electrolytes. The many-particle generalized Smoluchowski equation is formally reduced to a hierarchy of coupledn-particle equations. A closure relation, called the Instantaneous Relaxation Approximation (IRA), is used to decouple the equation for the one-particle self-propagator. Introducing also a mean field approximation (MFA), we recover the SPB equation. The accuracy of the IRA and MFA is quantitatively assessed for a model system consisting of two parallel uniformly charged plates with an intervening solution containing point ions in a dielectric medium. This is done by comparing diffusion propagators, survival probabilities and mean first passage times obtained by (1) solving the many-particle generalized Smoluchowski equation by the stochastic dynamics simulation technique (2) numerically solving the one-particle Smoluchowski equation with the exact (simulated) equilibrium potential of mean force, and (3) analytically solving the SPB equation. The IRA is found to be a useful approximation, whereas the MFA can lead to substantial error for systems with strong Coulomb coupling, as in the case of polyvalent counterions. Provided with a realistic potential of mean force, the one-particle Smoluchowski equation thus yields an accurate description of ion diffusion in non-uniform electrolytes.

ISSN:0026-8976    

DOI:10.1080/00268978600100801

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A single-crystal E.S.R. and multi-nuclear ENDOR study of the mixed ligand complex tetra-n-butylammonium(maleonitriledithiolato)(monoethyldithiophosphato)cuprate(II), diamagnetically diluted by the corresponding Ni(II) complex, and the crystal structure of the host complex are reported. n-Bu4N[Ni(mnt)(HEtdtp)].0·7 acetone is triclinic, space group P1, Z = 2 witha= 9·029(2),b= 13·432(4),c= 17·246(5) Å, α = 108·9(1), β = 90·2(1) and γ = 109·4(1)°. The spin-hamiltonian parameters are calculated from the results of an extended Hückel molecular orbital calculation. The experimentalg-tensor and the copper and the four sulphur hyperfine coupling tensors are reporduced well. The almost isotropic and unexpectedly large coupling of the phosphorous atom is negative, which can be understood qualitatively from a spin polarization mechanism.

ISSN:0026-8976    

DOI:10.1080/00268978600100811

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The effects of centrifugal distortions on polarizability anisotropies are taken into account to explain the experimental Rayleigh spectrum of H2S. Centrifugal corrections are calculated following a first-order perturbation theory due to Toyamaet al.The simulated spectrum agrees with the experimental one qualitatively, but the calculated corrections to the rotational transitions are not large enough to reproduce the experimental findings. Possible origins of that discrepancy and consequences of a significant variation of the optical anisotropy are briefly discussed.

ISSN:0026-8976    

DOI:10.1080/00268978600100821

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The maximal entropy distribution determined from a generalized variational principle is shown to have global properties and to be continuously connected to an arbitrary distribution with its own Lagrange multipliers even when both the distribution and the multipliers are considered as variational parameters.

ISSN:0026-8976    

DOI:10.1080/00268978600100831

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The aim of this paper is twofold. We wish to explain and test an analytical method for calculating the matrix elements of linear operators, that simplifies the numerical calculation to mere bookkeeping. The method has been described in Huber, D., 1985,Int. J. quant. Chem.,27, 245 [1] and applied there to the general Watson-rotation-vibration hamiltonian for non-linear molecules. In this paper we want to show that the method can also be used in more complex cases. As an example we present an application to the calculation of the first electronic transition in Li2H. The second aim is to report a calculation of the absorption spectrum of Li2H and the discussion of its rotation-vibration states.

ISSN:0026-8976    

DOI:10.1080/00268978600100841

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

We calculate the second dielectric virial coefficient,Bϵ, of a fluid whose molecules are sticky hard spheres with embedded central point dipoles. The effect of stickiness is to increasesBϵmarkedly.

ISSN:0026-8976    

DOI:10.1080/00268978600100851

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

This algorithm for the calculation of the induced multipole tensors in a set of charge distributions includes the contributions of partial derivatives of arbitrary order of the potentials defined by both induced and permanent multipoles as well as non-uniform external fields of arbitrary strength. Specific equations are given for both systems with and without translational order. The algorithm, which is based on the Maxwell invariant form, uses direct extensions of algorithms previously developed and tested for the calculation of permanent multipole energies and induced dipole vectors (when the non-uniformity of the field is neglected). The induced tensor components are calculated iteratively. The first approximation, which gives the components as the solution of a set of simultaneous linear equations, includes all nonlinear, non-uniform contributions of permanent multipoles and external fields as well as all contributions linear in derivatives of the induced potentials. The induced tensor components are then used to calculate the net induction energy. The general relations between the polarizability tensors with respect to a centre and the moments of the polarizability densities about the centre are derived.

ISSN:0026-8976    

DOI:10.1080/00268978600100861

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Reactive scattering of CH3radicals with ICl, IBr, I2and Br2molecules has been studied at an initial translational energyE∼ 30kJ mol-1, using a supersonic beam of CH3radicals seeded in He buffer gas. Laboratory angular and velocity distributions of CH3I and CH3Br product have been measured which show a gradation from short-lived complex dynamics for ICl to rebound dynamics for I2and Br2with intermediate behaviour for IBr. This variation in dynamics is attributed to the form of the potential energy surface which shifts from a shallow hollow for CH3+ ICl to repulsion in the exit valley for CH3+ I2, Br2, with both features being present for the intermediate case of CH3+ IBr.

ISSN:0026-8976    

DOI:10.1080/00268978600100871

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The site-site Ornstein-Zernike (SSOZ) equation with the hypernetted chain (HNC) closure is shown to effectively decouple for a class of model dipolar molecules. This means that the dipole-dipole interactions have little or no effect on the structure factor, although they significantly alter the short range site-site distribution functions. This result highlights a weakness in the practice of assessing the validity of a molecular model solely by comparing an experimental and theoretical structure factor.

ISSN:0026-8976    

DOI:10.1080/00268978600100881

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The intermolecular interaction ΔEin (NH3)2is investigated on the SCF level, with inclusion of correlation effects by means of the CPF method and within the simple test particle model. Whereas the linear hydrogen bonded structure is favoured on the SCF level, ΔE= -7·65 kJ mol-1, the most stable geometry on the highest level of theory is a cyclic structure, ΔE= -12·96 kJ mol-1. The minimum is very shallow and allows for appreciable angular motions. The test particle model reproduces the general features of ΔEbut shows deviations in details. The computed potentials are used in MD simulations to compute static and dynamic properties of liquid NH3. Good agreement with available experimental results is obtained throughout.

ISSN:0026-8976    

DOI:10.1080/00268978600100891

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor