Temperature dependence of the diffusion coefficient in liquid alkali metals

The temperature dependence of the diffusion coefficient of liquid alkali metals is studied along a constant volume line and the liquid-gas coexistence curve as well. Molecular-dynamics simulations are Used to Compute the velocity autocorrelation functions from which the self-diffusion coefficients are deduced. Along both lines of transformation, the Arrhenius law appears to he unable to fit the temperature dependence whatever be the alkali element. The numerical results obtained for different values of density and temperature are in good agreement with experiments near the melting point and can be interpreted in terms of a power law at higher temperatures.