Crystal imperfections are classified as follows:
1) Point Defects(0D Imperfections)
i) Vacancy Defect
ii) Schottky defect
iii) Self-Interstitial defect
iv) Frenkel defect
2) Line Defects (1D Imperfections)
i) Edge dislocation
ii) Screw Dislocation
3) Surface Defects (2D Imperfection)
i) Grain boundaries
ii) Tilt boundaries
iii) Twin boundaries
iv) Stacking faults
4) Volume Defects (3D Imperfections)
1) Whenever a layer of atoms is half inserted into the crystal lattice, the adjacent layers get shifted at the position of insertion and creates dislocation of other layers, such dislocation is known as edge dislocation.
2) The insertion of such layer of atoms create a stress concentration in that region, it also affects the density at that region.
3) It is measured by burger vector, and burger vector is in the plane of dislocation.
4) Due to such insertion, the successively bonds are break and formed transferring the squeezing effect due to extra layer and creates a permanent shear amongst the atoms.
5) The atoms rearrange themselves so as to nullify the squeezing of atoms and layers get separated.
1) When a layer of crystal structure is partially slides over other creating shear between layers is known as screw dislocation.
2) The layer slide over other in spiral form making shape of it like screwing form so it is named as screw dislocation.
3) The burger vector measure the intensity of dislocation and it is parallel to plane of dislocation.