The polarization energy of a complex is calculated for all alkali halides crystals containing Eu++ impurities. Up to 48 nearest neighbors of the complex are considered, and assumed that the field on each dipole is the one produced by the charge of the complex and by the field produced by the other induced dipoles. The results show that there are no significant changes in all alkali halides when going from second t o fourth-order. Therefore, i t is not necessary to take into account a large number of neighbors when calculating the polarization energy. This is a very important result since a low symmetry defect is considered.Die Polarisationsenergie eines Komplexes wird fur alle Alkalihalogenidkristalle, die Eu++-Storstellen enthalten, berechnet. Bis zu 48 niichste Nachbarn des Komplexes werden einbezogen urid es wird angenommen, da13 das Feld uber jeden Dipol von der Ladung des Komplexes und von den anderen induzierten Dipolen hervorgerufen wird. Die Berechnungen zeigen, da13 es keine signifikante dnderung in den Alkalihalogenidkristallen gibt, wenn von der zweiten zur vierten Ordnung ubergegangen wird. Deshalb ist es unnotig, eine grooe Anzahl von Nachbarn in Betrncht zu ziehen, wenn die Polarisationsenergie berechnet wird. Dieses Resultat ist sehr wichtig, da ein Kleinsymmetriedefekt angenommen wird.

The optical absorption of the Fd center in KCl: Ca2+ is studied by using point‐ion and ion‐size correction models. For the calculations the Gourary and Adrian wave function types I, II, III and Gaussian functions are used. The principal axes are obtained for several positions of the impurity‐vacancy dipoles, and the corresponding ground and excited states of the Fd center are calculated. Good agreement with the experimental values is found for the Gourary and Adrian wave functions of type I.

The shift with concentration variation of the optical absorption FA band in KCl-KBr mixed crystals, with Li impurities is studied by means of the method of Bartram et al. (1968). The distortion around the FA centre is calculated considering the change in the repulsive and polarisation energies due to the impurity. The energy due to this distortion is obtained by a perturbative method. This correction gives good agreement with the experiment values for one of the two absorption bands of the FA centre, but not for the other. Calculations using several types of wavefunction are in approximate agreement with the experimental observations of Asami and Ishiguro (1986).

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