Self-diffusion in liquid metals

Self-diffusion in liquid metals is investigated using the hydrodynamic mode l based Stokes-Einstein equation, and the hard sphere model. Based on a stu dy of sixteen liquid metals over a range of temperatures, it is found that the Stokes-Einstein predictions are satisfactory provided a temperature dep endent atomic diameter is used. Attempts to fit the self-diffusivity data t o D mu(p)/T = a constant using the temperature independent Goldschmidt diam eter yielded values of p ranging from 0.62 to 1.56 for the sixteen metals s tudied. Extensive calculations were performed in the case of liquid sodium based on the hard sphere model using three different expressions, based on the Enskog theory and corrections to it, for the diffusion coefficient. The effective hard sphere diameter appearing in these expressions was calculat ed as per the three well-known prescriptions based on perturbation theory a nd using two different inter-particle potentials. The hard sphere model, ap art from not providing satisfactory numerical accuracy, predicts a much wea ker temperature dependence of the self-diffusion coefficient than is observ ed experimentally. (C) 2000 Elsevier Science B.V. All rights reserved.