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

Sudheer Ganisetti; Anuraag Gaddam; Rajesh Kumar; Sathravada Balaji; Glenn C. Mather; Maria J. Pascual; Margit Fabian; Renée Siegel; Jürgen Senker; Vladislav V. Kharton; Julien Guénolé; N. M. Anoop Krishnan; José M. F. Ferreira; Amarnath R. Allu

doi:10.1039/C9CP04332B

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

Sudheer Ganisetti,^a Anuraag Gaddam,^b Rajesh Kumar,^c Sathravada Balaji,

^d Glenn C. Mather,

^e Maria J. Pascual,

^e Margit Fabian,

^f Renée Siegel,^g Jürgen Senker,

^g Vladislav V. Kharton,^h Julien Guénolé,ⁱ N. M. Anoop Krishnan,

*^d José M. F. Ferreira

*^c and Amarnath R. Allu

*^d

Author affiliations

* Corresponding authors

^a Department of Materials Science and Engineering, Institute I, Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstr. 5, 91058 Erlangen, Germany

^b Department of Materials and Ceramic Engineering, CICECO, University of Aveiro, 3810–193 Aveiro, Portugal

^c Department of Civil Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, India 110016
E-mail: jmf@ua.pt
Fax: +351-234-370204
Tel: +351-234-370242

^d Glass Division, CSIR-Central Glass and Ceramic Research Institute, Kolkata, India
E-mail: aareddy@cgcri.res.in, krishnan@iitd.ac.in
Fax: +91-33-24730957
Tel: +91-33-23223421

^e Instituto de Cerámica y Vidrio (CSIC), C/Kelsen 5, Campus de Cantoblanco, 28049 Madrid, Spain

^f Centre for Energy Research, Hungarian Academy of Sciences, 1121 Budapest Konkoly-Thegest. 29-33, Hungary

^g Inorganic Chemistry III, University of Bayreuth, 95440 Bayreuth, Germany

^h Institute of Solid State Physics RAS, 142432 Chernogolovka, Moscow District, Russia

ⁱ Institute of Physical Metallurgy and Materials Physics, RWTH Aachen University, 52056 Aachen, Germany

Abstract

Exploring the reasons for the initiation of Al–O–Al bond formation in alkali-earth alumino silicate 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 38.7CaO–9.7MgO–12.9Al₂O₃–38.7SiO₂ (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 is 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 conditions necessary for the formation of less favourable bonds are attributed to the presence of a high amount of modifier cations in current CMAS glass and their preferable coordination.

Physical Chemistry Chemical Physics

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

Abstract

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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

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