The unusual behaviour of EPR spectra of g-irradiatedtitania bearing sodium silicate glasses with various contents of titania werequalitatively interpreted on the base of model molecular orbital calculations.As a model of the actual paramagnetic particles were chosen the clusters whichindemnify the reasonable compromise between the model of cluster and exactnessof calculation used. The results of the quantum chemical calculations show thepreferential sensibitisation of Q2 unit in comparison with Q3unit (the largest electron density in the vicinity of non-bonding oxygens in Q2model). The bond strengths of Si-O bonds in the neighbourhood of non-bridgingoxygens show to the preferential substitution of Si4+ for Ti4+in the vicinity of the boundary of the cluster. The changes of the spin densitydistribution around the cluster after substitution of Si4+ for Ti4+(the largest delocalization) explain the unusual behaviour of the g-tensorcomponent with titania content in the glasses.
