Molecular Dynamics Analysis of Temperature Dependence of Liquid Metal Diffusivity

Abstract

The diffusivities of liquid Al, Co, Mg, Ni, and Pb have been calculated with molecular dynamics (MD)–based on semiempirical potentials derived from the second-moment approximation to the tight binding method (TBM-SMA). The liquid structure in terms of pair distribution function described in the present work agrees well with the available experimental data. The diffusion coefficients derived agree well with a limited number of experimental measurements. The calculated diffusivities were also compared with the predictions of available diffusion models, including the activated state model, the moving oscillator model, the density fluctuation model, the free volume model, and the scaling law proposed by Dzugutov. The present work substantiates the density fluctuation model, suggesting that diffusivity D possesses a square proportionality of temperature T2. It is concluded that diffusion is materialized in liquid metals through continuous movements of individual atoms over a small distance as a result of local density fluctuations rather than through discrete jumps of atoms over an interatomic distance.