The Fermi surfaces of the alkali metals

Long before direct experimental studies of the Fermi surfaces of the alkali metals became technically feasible, evidence had accumulated to suggest that their low-lying energy bands are almost free-electron-like. Indeed, the importance of the free-electron model in the development of the theory of metals owes much t o the coincidence that sodium, now known to be the most free-electron-like of all the alkali metals, was the subject of the pioneering cohesive energy calculations of Wigner and Seitz.¹