M interstitial cation in MG

This reaction starts from a solid containing M. It refers to reaction [2.R.15]. This creation involves two jumps and therefore two elementary steps. 

The voluminal speed of this elementary step can be written as (defects being diluted)  

Both the voluminal speeds are degenerated into zero and first order, respectively. 

The two preceding steps consider an equivalent step (see section 7.9) that can be written as  

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