  Crystal structures of simple metals and binary alloy phases based on the
close-packed hexagonal structure are analyzed within the model of Fermi
sphere-Brillouin zone interactions to understand distortions and superlattices.
Examination of the Brillouin-Jones configuration in relation to the nearly-free
electron Fermi sphere for several representative phases reveals significance of
the electron energy contribution to the phase stability. This approach may be
useful for understanding high pressure structures recently found in compressed
simple alkali and alkali-earth metals.
