QUALITATIVE MO TREATMENT OF THE GAMMA-INDUCED PARAMAGNETIC CENTERS INTITANIA BEARING SODIUM-SILICATE GLASSES

The Unusual behaviour of EPR spectra of gamma-irradiated titania beari ng sodium silicate glasses with various contents of titania were quali tatively interpreted on the base of model molecular orbital calculatio ns. As a model of the actual paramagnetic particles were chosen the cl usters which indemnify the reasonable compromise between the model of cluster and exactness of calculation used. The results of the quantum chemical calculations shaw the preferential sensibilisation of Q(2) un it in comparison with Q(1) unit (the largest electron density in the v icinity of non bonding oxygens in Q(2) model). The bond strengths of S i-O bonds in the neighbourhood of non-bridging oxygens show to the pre ferential substitution of Si4+ for Ti4+ in the vicinity of the boundar y of the cluster. The changes of the spin density distribution around the cluster after substitution of Si4+ for Ti4+ (the largest delocaliz ation) explain the unusual behaviour of the g-tensor component with ti tania content in the glasses.