The interaction of a cation vacancy and an anion vacancy in a CsCl lattice at the nearest-neighbour separation was investigated using the Dienes mode for the core distortion surrounding the vacancy pair. The formation energies of vacancy pairs in a family of seven crystals of CsCl type were evaluated to be 1.315, 1.208, 0.993, 1.007, 0.944, 0.691 and 0.698eV for CsCl, CsBr, CsI, TlCl, TlBr, NH4Cl and NH4Br, respectively.

Vacancy Pair Formation Energies in Crystals with the CsCl Structure. Y.V.G.S.Murti, C.S.N.Murthy: Journal of Physics C, 1972, 5[4], 401-7