Dynamic properties of liquid and undercooled aluminum.

First-principles molecular dynamics simulations of liquid and undercooled aluminum have been performed to study the evolution of dynamic properties across the melting point. Single-atom as well collective dynamic properties are determined and are related to the structural evolution of the liquid phase. The temperature dependence of the self-diffusion coefficient is computed from both the mean square displacement and the velocity autocorrelation function. Self-diffusion coefficients follow an Arrhenius law with the single activation energy of 250 meV, consistent with experimental results for the liquid phase. Moreover, we show that the Arrhenius relation can also be applied to the undercooled state at T = 875 K. Finally, a direct calculation of the shear viscosity from the transverse current correlation function shows that the Stokes-Einstein relation can be applied over the temperature range investigated.