Self-diffusion and microscopic dynamics in a gold-silicon liquid investigated with quasielastic neutron scattering.

We use incoherent quasielastic neutron scattering to study the atomic dynamics of gold in a eutectic Au₈₁Si₁₉ melt. Despite the glass-forming nature of this system, the gold self-diffusivity displays an Arrhenius behavior with a low activation energy characteristic of simple liquids. At high temperatures, long-range transport of gold atoms is well described by hydrodynamic theory with a simple exponential decay of the self-correlation function. On cooling towards the melting temperature, structural relaxation crosses over to a highly stretched exponential behavior. This suggests the onset of a heterogeneous dynamics, even in the equilibrium melt, and is indicative of a very fragile liquid. [ABSTRACT FROM AUTHOR]