Atom jumping activation volume

The quantity Vm, given by Eq. 7.26, is the difference between the volume of the system in an activated state and a well state. This volume difference is generally termed the activation volume for migration and is a positive quantity because of the atomic squeezing and resulting expansion of the system that occurs in the activated state. The activation volume can be measured experimentally by measuring the pressure dependence of the jump frequency, T. Find an expression for the pressure dependence of F and describe how it can be used to determine Vm. 

In a similar way we find jp p+]- Note that vy/p x is the (activated) jump frequency for the exchange of i with other component atoms (e.g., B, if / = A). Let us express Eqn. (5.101) in terms of volume concentrations and assume that the concentration differences between adjacent planes are small enough so that vp Wp = vp/p, is a valid assumption. If d is the distance between the planes, then... 

---