# Diffusion coefficient (Mass diffusivity) for solids

## Description

Diffusivity or diffusion coefficient is a proportionality constant between the molar flux due to molecular diffusion and the gradient in the concentration of the species (or the driving force for diffusion). The diffusion coefficient in solids at different temperatures is generally found to be well predicted by the Arrhenius equation.

Related formulas## Variables

D | diffusion coefficient (m^{2}/s) |

D_{0} | maximal diffusion coefficient (at infinite temperature) (m^{2}/s) |

E_{A} | activation energy for diffusion (J) |

k | Boltzmann constant |

T | absolute temperature (K) |