Self-diffusion in single component liquid metals: a case study of mercury

We report the temperature dependent atomic dynamics in mercury investigated with quasi-elastic neutron scattering between 240 and 350 K. The self-diffusivity follows an Arrhenius behavior over the entire investigated temperature range, with an activation energy of 41.8 +/- 1.4 meV. The standard deviation is in the order of 5%, significantly more precise than previously reported measurements in the literature. Similar to alkali metal melts, the self-diffusion coefficient close to the melting point can be predicted with an effective atom radius of 1.37 angstrom. This shows a dominant contribution from the repulsive part of the interatomic potential to the mass transport. We observed deviations from the Stokes/Sutherland-Einstein relation and indications of an increasing collective nature of the dynamics with decreasing temperature. Thus, a transport mechanism of uncorrelated binary collisions cannot fully describe the temperature dependence of the self-diffusion.