diffusion in the crystal otherwise solid state diffusion (rus. диффузия в кристалле) — particle transport in a crystalline solid due to random thermal motion.

Description

Diffusion can involve the lattice atoms (self-diffusion or homodiffusion), and atoms or ions of other chemical elements present in the crystal lattice (impurity or heterodiffusion), and point defects of crystal structure – interstitials and vacancies.

The main mechanisms of diffusion in solids are:

- vacancy mechanism, which involves the migration of atoms from a lattice position to an adjacent vacancy. Any crystal contains vacancies (vacant positions in the crystal lattice). One of the neighbouring atoms can jump to the vacancy site and leave a vacancy in its previous position. Thus atoms and vacancies move in the lattice causing mass transfer, whose intensity increases with the increasing number of vacancies;

- interstitial mechanism, in which the substance is transferred by interstitials. Such diffusion can be intense, if the crystal for some reason contains a large number of interstitials and they can easily move through the lattice;

- direct exchange involving two adjacent atoms merely exchanging places in the lattice.

Any process of diffusion in a solid usually involves all of these mechanisms, although their proportions can be different. The energy required to move a vacancy or an atom in the lattice is called the activation energy of diffusion. If a crystal contains extended defects (dislocations, stacking faults, grain boundaries), then the rate of migration in the area of these defects may be much higher than that in a defect-free area.

Authors

  • Zotov Andrey V.
  • Saranin Alexander A.

Source

  1. Atomic diffusion // Wikipedia, the free encyclopedia. — http://en.wikipedia.org/wiki/Atomic_diffusion (reference date: 12.12.2011).

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