Temperature dependent next-neighbour dynamics of liquid lead

The temperature dependence of the density correlation function at next-neighbour distances has been investigated for the liquid metal lead. This correlation function is a sensitive parameter for changes in the local environment and its Fourier transform was measured in a coherent inelastic neutron scattering experiment. The zero-frequency amplitude related to the long time decay of density fluctuations decreases in a nonlinear way and indicates a change in dynamics above the melting point. The derived generalized longitudinal viscosity shows a decrease near this temperature range. From these observations we suppose that solidification sets in on a microscopic level distinct above the melting point