Determination of Atomic Distributions in Liquid Lead-Bismuth Alloys by Neutron and X-Ray Diffraction

Abstract

The intensity of scattered neutrons and x‐rays has been measured for molten alloys and pure components in the system lead‐bismuth. A specially designed diffraction spectrometer has been constructed for the x‐ray determinations. The diffraction data have been treated to give atom distributions, and the first main peak in the distribution curves for solutions up to about 60 wt % bismuth corresponds to 12 nearest neighbors, with the value falling to about 7.7 for pure bismuth. No unusual features have been found in the eutectic region, but the density decrease on melting of lead‐rich solids is puzzling in view of the retention of 12 nearest neighbors at a mean distance shorter than in the crystal. A model of average pentagonal dodecahedral coordination is suggested to account for this and for the spacing of first maxima in the distribution curves.