Solute diffusion in liquid metals

The diffusion of several solutes in liquid silver and tin is discussed in terms of the fluctuation model, the modified critical fluctuation theory and the ‘hole’ theory of liquid diffusion, assuming the solute as a point charge equal to the difference in the charge of the solute and solvent atoms. The additional coulombic interaction of the solute was calculated in terms of the Thomas-Fermi approximation. In addition, the temperature dependence of solute diffusion in liquid tin is also evaluated from the self-consistent Hartree potential around an impurity charge. The theoretical and experimental values of relative diffusivity and its temperature dependence for various solutes, Ru, Co, Au, In, Sn and Sb, in liquid silver are in good quantitative agreement. Ru and Co in liquid silver appear to diffuse with effective valences of about -2 and zero, respectively.

The theoretical evaluation of solute diffusion in liquid tin provides only a qualitative agreement with the experimental data. The results obtained by use of the two potentials—the Thomas-Fermi and self-consistent Hartree potential around an impurity charge—are contrary to each other and provide only a qualitative agreement with the data on electromigration of various solutes in liquid tin.