The structure of liquid lead: EXAFS and MD studies

Accurate L-edge EXAFS (Extended X-ray Absorption Fine Structure) measurements of liquid Pb have been collected and analyzed using an advanced data-analysis technique (GNXAS) based on exact spherical wave multiple-scattering calculation of the absorption cross-section. Structural models obtained using molecular-dynamics (MD) simulations with an empirical and an embedded-atom potential, as well as structural data on liquid lead obtained from neutron and X-ray diffraction by other authors, have been put to a test using our new experimental results. The empirical two body potential, originally designed for the liquid state, reproduces quite accurately our experimental results. At the same time, the embedded atom potential, originally designed for the solid state, has turned out to inappropriately reproduce the first-neighbor g(r) peak. A comparison with previous XD and ND studies has shown that EXAFS analysis can improve our knowledge of the first-neighbor distribution. Previous observations of an apparent reduction in the coordination number in liquid Pb detected by EXAFS are briefly discussed.