Simulations of atomic structure, dynamics, and self-diffusion in liquid Au

Static and dynamic properties of liquid Au are studied with molecular-dynamics and Monte Carlo simulations, using a many-body potential based on the effective-medium theory. In order to address the outstanding question about the temperature dependence of the self-diffusion coefficient (Linear, exponential, and other dependencies have been proposed in the literature), simulations are performed in a dense temperature mesh up to the boiling point (3080 K). The liquid structure at various temperatures is described in terms of the pair distribution function, which is compared with x-ray data. Computed thermodynamic properties are in good agreement with experiment. Dynamic properties are represented by the velocity correlation function and self-diffusion coefficients of high accuracy. The temperature dependence of the diffusivity is qualitatively compared with several theoretical model predictions. A proportionality of the diffusion coefficient to the square of the temperature is found, in agreement with recent microgravity experiments on other nonsimple liquids. An analysis is made of atomic trajectories and the velocity correlation function at various temperatures, to provide physical arguments for and against different diffusion models in liquids. One of the results of this study is that it opposes diffusion processes with a single nonzero activation energy of, e.g., Arrhenius type. A discussion on this topic is included.