Imperfections in Crystal Structure: Point, Line and Plane Defects

Crystal defects are imperfections or deviations from the periodic arrangement of crystal constituents in otherwise ideally perfect crystals.

Point defects occur when atoms are missing, displaced, or in excess, disrupting the ideal structure of the crystal.

These deviations can result from imperfect packing during crystallization or from thermal vibrations at elevated temperatures.

Schottky and Frenkel defects are common examples of point defects, with metal excess and metal deficiency defects being less prevalent.

Line defects, or dislocations, disrupt the crystal's regularity along a line, reducing its long-range order.

An edge dislocation causes a misalignment of layers because a plane of atoms or ions stops their growth at a particular line within the crystal's interior.

Conversely, screw dislocations resemble a spiral ramp and serve as crystal growth sites.

Plane defects are stacking errors, like a hexagonal close-packed crystal containing a few planes with cubic close-packed packing.

These are commonly found on crystal surfaces or at the interfaces of two smaller crystals within a larger solid.