Point Defects on Crystal Lattice

An ideal crystal has each atom of the same type in the correct position. Usually, such an ideal structure does not exist. Crystals tend to have defects. Crystal defects can be divided into basic classes. Here you can see some of the point defects, which are places where an atom is missing or is irregularly placed in the lattice structure. Point defects include lattice vacancies, self-interstitial atoms, substitution impurity atoms, and interstitial impurity atoms. Then there also are linear defects. Those are defined by groups of atoms in irregular positions. Linear defects are commonly called dislocations. Lastly, there are planar defects, which are discontinuities between homogeneous regions of the material. Planar defects include grain boundaries, stacking faults and external surfaces.