point defect

"Point defect" is defined as atomic-size defect. In particular, when no atom exists at a lattice point, this defect is called "vacancy type point defect." On the other hand, when an atom is introduced into a position other than a lattice point, the defect is termed "interstitial type point defect." Vacancies can exist in a crystal at the thermal equilibrium state and play an important role for diffusion of atoms. Interstitial atoms are normally impurity atoms, but they can be the same atoms of the crystal when the atoms at the lattice points are ejected by irradiating the crystal with high-energy particles. In the latter case, since the interstitial atoms are easy to move, the atoms are likely to disappear by recombination with vacancies.