Point defects play a crucial role in the diffusion processes within crystalline solids. This significance stems from two primary characteristics. Firstly, point defects possess the ability to traverse the crystal lattice and facilitate the diffusion of atoms, essentially acting as carriers for this process. Secondly, these defects exist in a state of thermal equilibrium. In a crystal without defects, the mass and charge density exhibit periodicity in accordance with the lattice structure. The introduction of a point defect disrupts this periodicity. In metals, the conduction electrons effectively screen defects, resulting in uncharged point defects within the metal.