Abstract
Lattice spacings have been obtained for the hexagonal close-packed structures in lead alloys containing 27.0 to 32.0 at.% bismuth, which were rapidly cooled from the melt. Axial ratios for these structures vary from 1.653 to 1.654. By extrapolation to pure lead of these volume/atom determinations and of some activity data, the free energy of hexagonal close-packed lead relative to the face-centered cubic form is estimated. It is suggested that the structure of the lead polymorph stable at pressures greater than 0.16 Mbar is hexagonal close-packed.