Rate of an elementary jump

To calculate the rate of the jttmp, we can fully adopt the same logic as in Chapter 10. If we choose to represent the reactivity of the elementary step as a function of the concentration [5] in default at the initial position, we have  

Thus we can use relation [10.39], The coefficient a = A is justified in the case of energetic equivalence at the starting and arrival points  

Our defect is considered in the same way in the solid as in the solution, so we can apply the same changes to the model if the solution is not pure. The only difference is that in our case the constant k, which is related to the concentration, is defined directly from the diluted solution rather than the mixture in the gas. 

In the case of solid phases we prefer to use the reactivity per unit of area of the plane perpendicular to the path of reaction instead of the volume reactivity. We easily pass from one to another by multiplying the previous rate coefficient by the distance between the planes, which is of the same order of magnitude as the lattice parameter. 

We therefore use relation [10.22] in both area and volume, the rate coefficient being a coefficient as appropriate per unit area and surface reactivity or per unit of volume and volume reactivity. 

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