DIFFUSION

DIFFUSION [model keyword] [phase name] [additional parameter(s)] !

This keyword specifies the type of diffusion model to use for a phase if the default model is not desired. The default model calculates the full diffusion matrix. A diffusivity is calculated from the different mobilities and the thermodynamic factors. The former ones are calculated as:

M = exp (åMF/RT) exp (åMQ/RT) / RT

where å stands for a weighted summation of the different MF’s and MQ’s plus possibly a Redlich-Kister term.

Valid Model Keywords

Keyword	Description
NONE	No diffusion in this phase
DILUTE	Constitution list of dependent species in each sublattice must be given as an additional parameter. Only the diagonal terms in the diffusion matrix are calculated. D = exp (å DF/RT) exp (åDQ/RT).
SIMPLE	Constitution list of dependent species in each sublattice must be given as additional parameter. Only the diagonal terms in the diffusion matrix are calculated. D = å DF + å DQ.
MAGNETIC	The so-called ALPHA and ALPHA2 parameters must be given as additional parameters. ALPHA is for the substitutional magnetic model and ALPHA2 for the interstitial one. By appending an `&` sign and a species name after the alpha keyword one can supply individual values for the different species. The full diffusion matrix is calculated.