Defect interactions in ionic fluorite structures. II. 2:2:2 clusters in CaF2doped by YF3

Abstract

For pt.I see ibid., vol.8, p.2199 (1975). The mass action equilibrium between neutral defect pairs and neutral 2:2:2 clusters was studied for Y³⁺-doped CaF₂ using the theoretical value of the binding energy. The equilibrium for formation pairs from anion interstitials and substitutional Y³⁺ ions was included. The coulomb interactions of the 2:2:2 clusters among themselves and with the other species was allowed for in a second virial coefficient approximation for an idealized model at concentrations up to 5-6%. It was concluded that the effects were sufficiently small that at higher concentrations the statistical mechanics is likely to be dominated by the formation of larger clusters rather than by the slight ordering effect of the coulombic interactions between 2:2:2 clusters studied here.