Ab-initio study of structural, vibrational and non-linear optical properties of TiO2-Tl2O-TeO2 glasses

This paper reports on a systematic first-principles molecular dynamics investigation of binary ( TlO 0 . 5 ) y − ( TeO 2 ) 1 − y and ternary ( TiO 2 ) x − ( TlO 0 . 5 ) y − ( TeO 2 ) 1 − x − y tellurite glasses. The obtained structural models are validated against available measured X-ray pair distribution functions. In the binary system, increasing TlO 0.5 content induces network depolymerization through the reduction of Te coordination number, the substitution of Te–O–Te bridges with Te=O − ⋯ Tl + units, and the proliferation of non-bridging oxygens. In addition, rings analysis demonstrates a loss of the network connectivity via the opening of small n-membered rings. In contrast, TiO 2 acts as a network former in ternary glasses, preserving Te coordination number, and promoting a high fraction of bridging oxygens. Ti atoms induces a network repolymerization that manifests through the formation of smaller Ti-containing n-membered rings thereby balancing the strong effect of Tl 2 O modifier. Beside the structural analysis, we also computed Raman spectra and non-linear optical properties on the obtained large periodic models. Our results reproduce experimental trends in Raman band shifts with composition, while nonlinear optical calculations show that 〈 χ ( 3 ) 〉 remains stable with TlO 0.5 addition in binary glasses, consistent with experiment. In the case of ternary systems, we find that the inclusion of a small fraction of TiO 2 preserves the high optical nonlinearity of the TeO 2 network while maintaining the overall network connectivity. These results establish a predictive framework for tailoring the atomic structure and nonlinear optical response of tellurite glasses through the controlled interplay of the nature and concentration of modifiers. • TlO 0.5 breaks Te–O–Te bridges, while TiO 2 restores network connectivity in tellurite glasses. • Computed Raman spectra match experiments, revealing structural changes with Tl/Ti modifier concentrations. • χ 3 stability with TlO 0.5 addition highlights structure–property relationships in tellurite glasses.