  We show that the values of the defect entropy and the defect enthalpy for the
vacancy formation in diamond, have a ratio which is comparable to the one
predicted by a model suggested four decades ago. This model, which
interconnects the formation Gibbs energy with the bulk elastic and expansivity
data, has been also recently found of value in high $T_c$-superconductors as
well as in glass-forming liquids.
