Ceramics-Silikáty 40 (4) 137-143 (1996) 

P. Pelikán, M. Liška

The unusual behaviour of EPR spectra of g-irradiated titania bearing sodium silicate glasses with various contents of titania were qualitatively interpreted on the base of model molecular orbital calculations. As a model of the actual paramagnetic particles were chosen the clusters which indemnify the reasonable compromise between the model of cluster and exactness of calculation used. The results of the quantum chemical calculations show the preferential sensibitisation of Q² unit in comparison with Q³ unit (the largest electron density in the vicinity of non-bonding oxygens in Q² model). The bond strengths of Si-O bonds in the neighbourhood of non-bridging oxygens show to the preferential substitution of Si⁴⁺ for Ti⁴⁺ in the vicinity of the boundary of the cluster. The changes of the spin density distribution around the cluster after substitution of Si⁴⁺ for Ti⁴⁺ (the largest delocalization) explain the unusual behaviour of the g-tensor component with titania content in the glasses.

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