An ionic solid is in thermal equilibrium at temperature T. In order to maintain the charge neutrality, vacancy defects are created in pairs (+ve and –ve ions). N is the number of molecules per unit volume and n is number of vacancies per unit volume. If you plot ln( ???? ???? ) as a function of 1/T what will be the nature of the curve? How can one determine the energy required for creating a Frenkel (vacancy) defect from such a curve? Answer in not more than two lines.