Structure of liquid lithium

Abstract

Neutron diffraction experiments, made at a steady-state reactor source, were used to study the structure of liquid 7Li at temperatures of 197, 452 and 595 °C. A careful data analysis procedure was undertaken in which specific issues taken into account include (i) the influence of Brillouin modes on the measured diffraction pattern at small scattering vectors, (ii) inelasticity corrections that are significant for light atom systems, such as lithium, and (iii) the effects caused by the diffractometer resolution function. Data sets taken for the same liquid temperature using different incident neutron energies yield ion–ion partial structure factors, SII(k), that are in agreement within the statistical errors. The SII(k) are compared with previous experimental results and with the results obtained from liquid state theory and molecular dynamics methods made using several different local pseudopotentials. Finally, the valence electron form factor, ρ(k), is estimated by combining SII(k) with x-ray diffraction data and the ion–valence electron partial structure factor, SIe(k), is calculated by combining SII(k) with the ρ(k) obtained from both experiment and theory. The results show that the extraction of ρ(k) and SIe(k) by a combination of neutron and x-ray diffraction methods is feasible in practice, but demonstrates a need for new x-ray diffraction experiments on liquid lithium.