The measurement of self-diffusion coefficients in liquid metals with quasielastic neutron scattering

Abstract

Quasielastic incoherent neutron scattering (QENS) has proven to be a versatile tool to study self diffusion of atoms in liquid metals. Here it is shown, that coherent contributions to the signal in the small q limit appear as a flat and energy independent constant to the QENS signal in single-component liquid metals even for systems with a samll incoherent scattering cross section, like aluminium. Container-less processing via electromagnetic or electrostatic levitation devices, espacially designed for QENS, enables the in-situ measurement on liquid metallic droplets of sizes between 5 mm to 10 mm in diameter. This gives access of several hundred Kelvin below the respective melting point. Compared to experiments using a thin-walled crucible giving self-diffusion coefficient. QENS results of liquid germanium and germanium isotope mixtures, titanium, nickel, copper and aluminium are receiwed. The self-diffusion coefficeints of these systems are best described by an Arrhenius-type temperature dependence around their respecitve melting points.