  Analysis of experimental data shows that the metal--insulator transition is
possible in materials composed of atoms of only metallic elements. Such a
transition may occur in spite of the high concentration of valence electrons.
It requires stable atomic configurations to act as deep potential traps
absorbing dozens of valence electrons. This means in essence that bulk metallic
space transforms into an assembly of identical quantum dots. Depending on the
parameters, such a material either does contain delocalized electrons (metal)
or does not contain such electrons (insulator). The degree of disorder is one
of these parameters. Two types of substances with such properties are
discussed: liquid binary alloys with both components being metallic, and
thermodynamically stable quasicrystals.
