[110] anion replacement sequences in alkali halides and their relation to F-centre production by electron-hole recombination

Abstract

In the previous paper it was shown that radiationless electron-hole recombination in alkali halides might provide energy for the formation of negative ion vacancies. A [110] replacement sequence provides an efficient method for separation of the interstitial from the vacancy and is particularly suitable for defect formation by electron-hole recombination. Two-body calculations of the replacement thresholds, including only short-range repulsive interactions, are discussed. A computer simulation of the [110] replacement sequence, including the effects of long-range Coulomb forces, has been carried out. The results of this simulation indicate that in many of the alkali halides, within broad limits of variation of the interaction forces, replacement thresholds are about 4-5 ev. In other alkali halides, such as NaI, much higher values are calculated, whilst the alkaline earth oxides give values of several tens of electron volts.