Datensatz

Zusammenfassung

High-resolution X-ray pair distribution functions for molten and glassy TeO₂ reveal coordination numbers n_TeO ≈ 4. However, distinct from the known α-, β-, and γ-TeO₂ polymorphs, there is considerable short-range disorder such that no clear cutoff distance between bonded and nonbonded interactions exists. We suggest that this is similar to disorder in δ-TeO₂ and arises from a broad distribution of asymmetric Te–O–Te bridges, something that we observe becomes increasingly asymmetric with increasing liquid temperature. Such behavior is qualitatively consistent with existing interpretations of Raman scattering spectra, and equivalent to temperature-induced coordination number reduction, for sufficiently large cutoff radii. Therefore, TeO₂ contains a distribution of local environments that are, furthermore, temperature dependent, making it distinct from the canonical single-oxide glass formers. Our results are in good agreement with high-level ab initio cluster calculations.