  Two models have been proposed for the interconnection of the defect Gibbs
energy g^i with bulk properties almost 60 and 30 years ago, respectively. The
one, proposed by Zener, assumes that g^i can be accounted for the work that
goes into straining the lattice and hence it is proportional to the shear
modulus of the solid. The other, considers that, since g^i corresponds to an
isobaric and isothermal process, it should be proportional to the isothermal
bulk modulus and the mean volume per atom. The results of these two models are
compared for different processes (defect formation, self-diffusion activation,
hetero-diffusion) in a variety of solids including metals (fcc, bcc and
tetragonal) as well as solids that exhibit superionic behavior. We find that
the latter model does better than the former.
