Estimation of the solute diffusion coefficient of a dilute liquid alloy: static structure factor and isothermal...

A simple method for estimating the mass diffusion coefficient of a dilute binary liquid alloy that sequentially uses experimental data for the static structure factor and isothermal susceptibility of the solvent is presented, as well as another using the static structure factor alone and a method using the isothermal susceptibility alone. A fourth method that simultaneously uses the static structure factor and isothermal susceptibility is also noted. Of significance is the fact that these methods do not require information about the interatomic potential. Stability with respect to weights in the optimization process employed has been established and is reported, as well as some indication of the upper limits on the applicable solute concentration. Comparisons are made with results from a high quality capillary experiment for Pb 1 wt% Au liquid alloy performed in microgravity, and with velocity autocorrelation estimates derived from molecular dynamics simulation. The results suggest that the capillary experiments are influenced by reverse diffusion of the solvent, and actually measure an average of the mass diffusion coefficients, D(ij), weighted by the equilibrium concentrations of the solvent, x(1), and solute, x(2), defined by [Formula: see text] The three methods are required to provide upper and lower estimates for the mixed solvent-solute diffusion coefficient, which is not directly accessible from the experimental data, and demonstrate agreement with the experiment via D(tot).