Heat capacity of disordered systems

5 Heat capacity of disordered systems Crystal defects 

Here A vac. S and A vacH are the molar entropy and enthalpy of formation of the defects. Using a pure metal like aluminium as an example, the fractional number of defects, heat capacity and enthalpy due to defect formation close to the fusion temperature are 5-10-4, 0.3 J K-1 mol-1 and 30 J mol-1 [30], 

In other cases more complex disordering mechanisms are observed. Non-stoichiometric oxides in which the oxygen vacancies are ordered at low temperatures illustrate convergent disordering. The oxygen atoms and oxygen vacancies are here distributed at the same sub-lattice at high temperatures. An example is 

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