Theoretical study of native and rare-earth defect complexes in beta-PbF2

Native and rare-earth-doped point-defects in beta-PbF2 are studied in the f ramework of the pair-potential approximation coupled with the shell model d escription of the lattice ions. For the perfect lattice, a new set of poten tial parameters are obtained which reproduce structure, elastic and dielect ric constants of PbF2 very well. The calculated formation energies for nati ve defects suggest that the anion Frenkel disorder is preferred over the ca tion Frenkel and Schottky-like disorder in PbF2. The computed temperature b ehavior of the ionic conductivity agrees very well with the available exper imental data. In the rare-earth doped PbF2, a site preference of the charge -compensating fluorine interstitial appears to change from nearest to next- nearest neighbor with the increase in the rare-earth ionic radius.