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Elucidating the formation of Al-NBO bonds, Al-O-Al linkages and clusters in alkaline-earth aluminosilicate glasses based on molecular dynamics simulations

Abstract

Exploring the reasons for the initiation of Al-O-Al bond formation in alkali-earth aluminosilicate glasses is a key topic in the glass-science community. Evidence for the formation of Al-O-Al and Al-NBO bonds in the glass composition 38.7 CaO - 9.7 MgO - 12.9 Al2O3 - 38.7 SiO2 (CMAS, mol%) has been provided based on Molecular Dynamics (MD) simulations. Analyses in the short-range order confirm that silicon and the majority of aluminium cations form regular tetrahedra. Well-separated homonuclear (Si-O-Si) and heteronuclear (Si-O-Al) cluster regions have been identified. In addition, a channel region (C-Region), separated from the network region, enriched with both NBO and non-framework modifier cations, has also been identified. These findings are in support of the previously proposed extended modified random network (EMRN) model for aluminosilicate glasses. A detailed analysis of the structural distributions revealed that a majority of Al, 51.6%, is found in Si-O-Al links. Although the formation of Al-O-Al and Al-NBO bonds are energetically less favourable, a significant amount of Al is found in Al-O-Al links (33.5%), violating Lowenstein’s rule, and the remainder is bonded with non-bridging oxygen (NBO) in the form of Al-NBO (Al-O-(Ca, Mg)). The necessary conditions for the formation of less favourable bonds are attributed to the presence of a high amount of modifier cations in the current CMAS glass and their preferable coordination.

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Publication details

The article was received on 05 Aug 2019, accepted on 03 Oct 2019 and first published on 03 Oct 2019


Article type: Paper
DOI: 10.1039/C9CP04332B
Phys. Chem. Chem. Phys., 2019, Accepted Manuscript

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    Elucidating the formation of Al-NBO bonds, Al-O-Al linkages and clusters in alkaline-earth aluminosilicate glasses based on molecular dynamics simulations

    S. Ganisetti, A. Gaddam, R. Kumar, S. Balaji, G. C. Mather, M. J. Pascual, M. Fabian, R. Siegel, J. Senker, V. Kharton, J. Guénolé, N. M. A. Krishnan, J. M. F. Ferreira and A. R. Allu, Phys. Chem. Chem. Phys., 2019, Accepted Manuscript , DOI: 10.1039/C9CP04332B

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