Atomic Transport in Liquids

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Abstract The topics discussed are: We conclude that along the saturated vapour pressure curve the temperature dependence of the shear viscosity coefficient, η, for liquid metals is not the same as that of its counterpart in the inert gas liquids, according to the available experimental data. In addition, for the data examined a power law in T is a more appropriate description than an Arrhenius expression. The situation is more confused for the self-diffusion coefficient, D. For the saturated liquid, a linear dependence can be claimed for Ar and some liquid metal data, but the evidence is not conclusive. To develop a coherent and comprehensive understanding of the transport mechanism more extensive diffusion data is essential. The representation of experimental atomic transport coefficient data in simple liquids with respect to temperature and density, the emphasis being on self-diffusion and shear viscosity. The theoretical framework and the derivation of expressions for the coefficients in terms of Green-Kubo integrands. Computer simulation data for the rigid sphere, Lennard-Jones and liquid metal-like systems. Rigid sphere dynamics and the rigid sphere fluid as a reference system for atomic transport in liquids. Mode-coupling theory and interrelationships between coefficients. We suggest, also, a more systematic approach to the determination of transport coefficients in computer simulation studies, particularly for liquid metal-like systems. On the theoretical front, in spite of an established framework, realistic calculations of atomic transport properties of liquids (on the scale required) are rare. Mode-coupling theory, we believe, offers the opportunity of progress here. We comment, finally, on interrelationships between coefficients and give a derivation of the Stokes-Einstein relation between D and η from a microscopic viewpoint.