What is the activation energy for diffusion

Activation energy

Activation energy, Activation barrier, generally an energy that must be applied in addition to enable a chemical or physical process.

1) chemistry: the excess amount of energy that is necessary beyond the average energy content of atoms or molecules to trigger a chemical reaction (physical chemistry). The term was introduced by S. Arrhenius. The excitation (activation) can take place thermally (through impacts) or through radiation absorption. The activation energy E.a (often with

labeled) itself is temperature-dependent in most reactions. This fact can be taken into account by the following formulation: E.a = RT2(∂lnk/∂T)V. It is R. the general gas constant, T the absolute temperature, k the reaction rate constant, and the index V means "at constant volume". In the course of the reaction, part of the activation energy used is usually released again as deactivation energy. The heat of reaction results from the difference between these two energies. The level of activation energy is decisive for the speed of the reaction. (Arrhenius law)

2) Solid state physics: additional energy required for diffusion. Diffusion in the solid is often described in the form of an Arrhenius law:

(D.: Diffusion coefficient, E.: Activation energy of the diffusion process, kB.: Boltzmann constant and T: Temperature). This is the classic idea of, for example Interstitial diffusion, in which atoms are on their way from one Interstitial space to the neighboring one Potential barrier the height E. must overcome (barrier height), this corresponds to the Migration energy. In case of Vacancy diffusion includes E. the sum of migration energy and Formation energy the blank. The activation energy is lower in the case of the incoherent tunnels (Tunnel effect) as well as the crowdion diffusion.

3) Semiconductor physics: the energy that a hole or electron needs to get into the conduction band. (Acceptor, donor)