CALCULATIONS ON RELAXATIONS DUE TO A VACANCY, BINDING-ENERGY OF A VACANCY VACANCY PAIR, AND FORMATION ENERGY OF A VACANCY IN THORIUM

The lattice statics method is used to calculate the relaxations due to vacancy created in a lattice. The measured phonon dispersion relations and the elastic constants are used as constraints to calculate the dynamical matrix considering interactions up to eighth neighbor. The calculation shows that the first three shells of atoms relax towards the vacancy. The divacancy binding energy is found to be 0. 477 ev which agrees well with simpler model calculation. Considering the uncertainty in the experimental value the agreement between the calculated and experimental value of the monovacancy formation energy is fairly good.