Short-range order in liquid Li–Pb alloys

Abstract

The neutron diffraction patterns of liquid lithium lead alloys containing 0, 17, 34, 48, 61, 80, and 100 at.% ⁷Li were measured. The long‐wavelength limit of the partial structure factors a_ij(k) and of the concentration–concentration correlation function S_CC(k) is calculated. These values agree well with the values calculated from activity data. For the 80 at.% alloy the total S_CC(k) function was measured. It shows a pronounced first peak at the k value of a prepeak observed with x rays. The Fourier tranform of S_CC(k) is related to the short‐range order‐size coefficients which have been introduced by Warren et al. (Ref. 19) to describe the local order of solid solutions. The data for the liquid Li–Pb alloys indicate a preference for unlike nearest neighbors and a reduction of the distance between unlike nearest neighbors as compared with the mean distance of the pure components. This short‐range order is probably due to a partially saltlike bonding between lithium and lead ions. The over‐all structure of the liquid alloys is similar to the structure of a hard sphere system.