title: Response to "Comment on 'A model for phosphate glass topology considering the modifying ion sub-network"' [J. Chem. Phys. 142, 107103 (2015)].
abstract: In our recent paper [C. Hermansen, J. C. Mauro, and Y.-Z. Yue, J. Chem. Phys. 140, 154501 (2014)], we applied temperature-dependent constraint theory to model the glass transition temperature (Tg) and liquid fragility index (m) of alkali phosphate glasses. Sidebottom commented on this paper concerning the m values obtained by differential scanning calorimetry (DSC) [D. L. Sidebottom, J. Chem. Phys. 142, ⬛ (2015)]. We have considered Sidebottom's comments carefully and conclude that the m values of phosphate liquids obtained by DSC are reliable, except for the NaPO3 and possibly P2O5 compositions. Based on his dynamic light scattering measurements, Sidebottom has found that P2O5 is a strong liquid with m ≈ 20. However, based on the heat capacity jump at Tg and the stretching exponent of the relaxation function, P2O5 should be classified as an intermediate fragile liquid with m ≈ 40. We also argue that m cannot be universally related to the average connectivity of the network and point out several inconsistencies with this view.
authors.affiliation: Section of Chemistry, Aalborg University, Fredrik Bajers Vej 7H, 9220 Aalborg, Denmark.
authors.forename: Christian
authors.initials: C
authors.lastname: Hermansen
authors.affiliation: Science and Technology Division, Corning Incorporated, Corning, New York 14831, USA.
authors.forename: John C
authors.initials: JC
authors.lastname: Mauro
authors.affiliation: Section of Chemistry, Aalborg University, Fredrik Bajers Vej 7H, 9220 Aalborg, Denmark.
authors.forename: Yuanzheng
authors.initials: Y
authors.lastname: Yue