A limit of validity of a 'basic' thermodynamical relation between activation enthalpy and entropy of diffusion and defect formation

This paper points out that a given equation is not the basic formula of thermodynamics itself, but holds obly in some restricted circumstances. It is shown that its validity becomes questionable when a total system is composed of a phonon system and a subsystem characterized by some internal degree of freedom sigma, and in addition, it takes much longer for the latter to attain thermal equilibrium as compared to the former. The paper deals specifically with an assembly of vacancies as an example of the subsystem of this nature: the time for vacancies to attain thermal equilibrium number is at least 10-6 s, being much longer than a typical phonon lifetime approximately equal to 10-10 s. A partially ordered structure is also discussed as another example of the subsystem of this nature. (Auth.)