Chemical localization
  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. 
V.F. Gantmakher