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crystal defects

...and the impurity type. The Frenkel defect involves a single ion, which is displaced from its normal lattice point and shifts to a nearby interstice, or space, between atoms in the lattice. In the
Schottky defect, two ions of opposite sign leave the lattice. Impurity defects are foreign atoms that replace some of the atoms making up the solid or that squeeze into the interstices; they are...

vacancy in solids

...that give colour to many solids. Vacancies can be created by mechanical deformation of the crystal, rapid cooling from high temperature, or the impact of radiation on the crystal. In the so-called
Schottky defect, an atom moves from the inside of the crystal to its surface, leaving behind an isolated vacancy. In the Frenkel defect, an atom moves to a new position between other atoms of the...