(2017). Modelling the sulfate capacity of simulated radioactive waste borosilicate glasses. Journal of Alloys and Compounds, 695,[656][657][658][659][660][661][662][663][664][665][666][667]. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Copyright and re-use policy M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT

The oxidation state, coordination, and local environment of sulfur in alkali silicate (R 2 O−SiO 2 ; R = Na, Li) and alkali/alkalineearth silicate (Na 2 O−MO−SiO 2 ; M = Ca, Ba) glasses have been investigated using neutron diffraction and Raman spectroscopy. With analyses of both the individual total neutron correlation functions and suitable doped−undoped differences, the S−O bonds and (O−O) S correlations were clearly isolated from the other overlapping correlations due to Si−O and (O−O) Si distances in the SiO 4 tetrahedra and the modifier−oxygen (R−O and M−O) distances. Clear evidence was obtained that the sulfur is present as SO 4 2− groups, confirmed by the observation in the Raman spectra of the symmetric S−O stretch mode of SO 4 2− groups. The modifier−oxygen bond length distributions were deconvoluted from the neutron correlation functions by fitting. The Na−O and Li−O bond length distributions were clearly asymmetric, whereas no evidence was obtained for asymmetry of the Ca−O and Ba−O distributions. A consideration of the bonding shows that the oxygen atoms in the SO 42− groups do not participate in the silicate network and as such constitute a third type of oxygen, "non-network oxygen", in addition to the bridging and non-bridging oxygens that are bonded to silicon atoms. Thus, each individual sulfate group is surrounded by a shell of modifier and is not connected directly to the silicate network. The addition of SO 3 to the glass leads to a conversion of oxygen atoms within the silicate network from non-bridging to bridging so that there is repolymerization of the silicate network. There is evidence that SO 3 doping leads to changes in the form of the distribution of Na−O bond lengths with a reduction in the fitted short-bond coordination number and an increase in the fitted long-bond coordination number, and this is consistent with repolymerization of the silicate network. In contrast, there is no evidence that SO 3 doping leads to a change in the distribution of Li−O bond lengths with a total Li−O coordination number consistently in excess of 4.

The results have been presented at various conferences: ❖ "Role of BaO as modifier in silicate and borosilicate glasses with high sulphate solubility", S. Vaishnav, A

2020). Composition-structureproperty effects of antimony in soda-lime-silica glasses. Journal of Non-Crystalline Solids.

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