Structural phase transitions in Na, Mg and Al crystals: dominant role of the valence in local pseudopotential theory

Abstract

Within a perturbative treatment of realistic local electron-ion pseudopotentials for the simple metals, we study structural phase transitions under pressure in Na and other monovalent metals, Mg and other divalent metals, and Al and other trivalent metals. For the "good local pseudopotential" metals Na, Mg, and Al, our results are in reasonable agreement with experiment. The sequence of predicted transitions between crystal structures, and the volume compression ratios V/V0 at which these transitions are predicted, are determined largely by the valence z. The valence z also determines the dependence of the total energy upon the tetragonal c/a ratio along the Bain path from bcc to fcc. This path shows the divalent metals unstable in both fcc and bcc structures, and the trivalent metals unstable in bcc.