Entropy of Formation of Vacancies in Ionic Crystals

Abstract
The effect of anharmonicity on the entropy of formation of vacancies is considered for three alkali halides. The Brauer method and Boswarva and Lidiard method have been used for evaluation of elastic displacement of the ions. It has been concluded that the anharmonic effects are small and that the Brauer method gives values in good agreement with experimental results. The Boswarva and Lidiard method gives a lower value of entropy of formation. Our findings are contrary to those of Roy and Ghosh.