Structure of TeO₂ Glass and Melt by Reverse Monte Carlo Simulations of High-Energy X-Ray Diffraction Data Sets

The short-range and medium-range structures of TeO₂ glass and melt are elucidated by Reverse Monte Carlo (RMC) simulations of High-Energy X-ray Diffraction data sets published in an earlier study by Alderman et al. (J. Phys. Chem. Lett.11(1) (2020)427-431). The RMC analysis reveals that there exists a wide range of Te-O bond lengths in both TeO₂ glass and melt short-range structures. The Te-O pair distribution function (PDF) of the melt has peaks centered at 1.87, 2.06, 2.35, 2.65, and 3.00 (±0.01) Å, whereas the corresponding peaks in the glass are at 1.91, 2.07, 2.28, 2.54, 2.77, and 3.00 (±0.01) Å. The Te-O partial PDF of the melt shows a peak at 2.35 Å, which is not present in the glass structure; therefore, the same co-ordination sphere radius of 2.36 Å cannot be used for calculating the Te-O co-ordination numbers in the TeO₂ melt and glass, as done in the earlier study by Alderman et al. Using a more appropriate radius of 2.41 Å for glass and 2.22 Å for the melt, the corresponding Te-O co-ordination numbers are found to be 3.99 and 3.33, respectively. The RMC analysis successfully determined the O-O pair distributions, which show the first peaks at 2.31-2.33 (±0.01) Å. Finally, Te-Te pair distributions show peaks at slightly longer distances in the melt compared to those in glass, and the melt is found to have greater medium-range disorder.