MIXED DIMERS IN RARE-EARTH-DOPED FLUORIDES

Dipole aggregation in rare-earth-doped fluorides, using the HADES code to calculate the energies of the defects was extensively studied. The binding energy values determined for dipoles and dimers agree quite w ell with published data. The possibility of creation of mixed dimers t ook into account the size of the impurities and also the electronic co nfiguration. The results obtained confirmed that binding energies depe nd upon the ionic radius of the impurities and revealed a preferential order for the formation of mixed dimers. For the impurities with ioni c radii larger than or very near to that for calcium the chance of for ming mixed dimers is greater than for smaller impurities. The obtained values of the energies confirm the possibility of mixed dimer creatio n although simple dimers are preferentially formed first.