  Binary alloy phases of the noble metals with main group elements are analyzed
in relation to body centered cubic structure with orthorhombic and hexagonal
distortions. Stability of these distorted phases is considered on the base of
the Fermi sphere - Brillouin zone interaction to understand the important part
of the band structure energy contribution to the overall crystal energy.
Examination of Brillouin zone - Fermi sphere configurations for several
representative phases has shown significance of the electron energy
contribution in the formation of distorted structures with superlattices and
ordered vacancies. This approach may be useful for understanding recently found
complex structures in compressed simple alkali metals.
