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Structural properties of molten silicates from ab initio molecular-dynamics simulations: comparison between CaO-Al$_2$O$_3$-SiO$_2$ and SiO$_2$

Magali Benoit·Simona Ispas·Mark E. Tuckerman
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Abstract

We present the results of first-principles molecular-dynamics simulations of molten silicates, based on the density functional formalism. In particular, the structural properties of a calcium aluminosilicate $ [$ CaO-Al$_2$O$_3$-SiO$_2$ $ ]$ melt are compared to those of a silica melt. The local structures of the two melts are in good agreement with the experimental understanding of these systems. In the calcium aluminosilicate melt, the number of non-bridging oxygens found is in excess of the number obtained from a simple stoichiometric prediction. In addition, the aluminum avoidance principle, which states that links between AlO$_4$ tetrahedra are absent or rare, is found to be violated. Defects such as 2-fold rings and 5-fold coordinated silicon atoms are found in comparable proportions in both liquids. However, in the calcium aluminosilicate melt, a larger proportion of oxygen atoms are 3-fold coordinated. In addition, 5-fold coordinated aluminum atoms are observed. Finally evidence of creation and anihilation of non-bridging oxygens is observed, with these oxygens being mostly connected to Si tetrahedra.

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Magali Benoit, Simona Ispas, Mark E. Tuckerman. 2001-09-19. Structural properties of molten silicates from ab initio molecular-dynamics simulations: comparison between CaO-Al$_2$O$_3$-SiO$_2$ and SiO$_2$. https://doi.org/10.1103/physrevb.64.224205

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