Nature of Self-Diffusion in Fluids


  • M. P. Malomuzh I.I. Mechnikov Odesa National University



self-diffusion coefficient, shear viscosity, molecular liquids


The nature of the self-diffusion in low-molecular fluids is discussed. The particular attention is paid to atomic fluids (such as argon), liquid metals, and associated fluids (such as water). The self-diffusion coefficient in the fluids of all indicated types is considered to be the sum of two components: one of them is associated with the transfer of molecules by hydrodynamic vortex modes, and the other is generated by the circulatory motion of local molecular groups. The both components have a collective nature, they are genetically related to each other and differ only by their scales: the former is mesoscopic, the latter is nanoscopic. Manifestations of the collective vortical transport of molecules as specific features in the time dependence of the root-mean-square displacement of molecules are discussed. Sound arguments are proposed concerning the inadequacy of the activation mechanism of thermal molecular motion in low-molecular liquids. The immanent contradiction of exponential temperature dependences for the viscosity and self-diffusion coefficients is proved. In all cases, the preference is given to qualitative arguments.


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How to Cite

Malomuzh, M. P. (2018). Nature of Self-Diffusion in Fluids. Ukrainian Journal of Physics, 63(12), 1076.



Physics of liquids and liquid systems, biophysics and medical physics

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