What is it about?

The paper presents the first experimental results on the coordination environment of magnesium under pressure in amorphous aluminosilicates that have important applications as commercial display glasses and significance as crustal and mantle materials.

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Why is it important?

The results show that the replacement of magnesia by alumina enhances the rate of increase of the Mg-O coordination number with pressure. They also lead to an equation of state that shows an anomalous minimum in the pressure dependence of the bulk modulus. The onset to this minimum marks a threshold for transitioning between a large bulk modulus at lower pressures, which promotes scratch resistance, and a smaller bulk modulus at higher pressures, which promotes fracture toughness. There is scope for tuning this threshold pressure via the glass composition and the chosen pressure and/or thermal treatment. The results also explain the appearance of distinct pressure-dependent structural transformation regimes in the preparation of permanently densified magnesium aluminosilicate glasses.


A key feature of the work was the employment of in situ high pressure neutron diffraction with isotope substitution. The findings demonstrate the value of this method as a tool for revealing the stucture of amorphous materials under extreme conditions.

Professor Philip S Salmon
University of Bath

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This page is a summary of: Pressure dependent structure of amorphous magnesium aluminosilicates: The effect of replacing magnesia by alumina at the enstatite composition, The Journal of Chemical Physics, February 2024, American Institute of Physics,
DOI: 10.1063/5.0189392.
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