Structure of Alkali Metals in the Liquid State

Abstract

Neutron diffraction patterns have been obtained for the alkali metal liquids; lithium (180°C), sodium (100°C), potassium (65°C), rubidium (40°C, 160°C, 240°C, and 360°C), and cesium (30°C, 300°C, and 575°C). It was found necessary to correct intensities for scattering by a free atom for lithium and sodium but not for the heavier atoms. Atomic distribution curves were computed for all the above cases, and compared with results from x‐ray diffraction. Just above melting temperatures the nearest‐neighbor distances are for lithium 3.15 A, sodium 3.82 A, potassium 4.64 A, rubidium 4.97 A, and cesium 5.31 A, the number of nearest neighbors is, within one‐half atom, about 9.0 to 9.5 atoms in each case. At elevated temperatures with rubidium and cesium, a weak subsidiary concentration of atoms appears between the usual first and second neighbor concentration.