The Coexistence of Unstable, Metastable, and Separated Frenkel Pair Defects in Solids. I. Basic Characteristics

The existence of unstable, metastable, and separated states of Frenkel pair defects as well as their coexistence in solids are theoretically studied. Existence region, lifetime, and equilibrium concentration of defects in these states are determined and a phase diagram of defect states for KBr is also drawn. The unstability (spontaneous annihilation) zone radius of charged and neutral pair defects are estimated. It is shown that this zone radius is very large for charged (particularly, for multiple charged) pair defects, while for neutral pairs it is about the interatomic distance. Unstable pair lifetime is estimated as ≈ 10−12 s, while metastable pair life strongly depends on crystal temperature and decreases rapidly with rising temperature. The results obtained are in good agreement with available experimental data.