What is it about?
We investigate the pressure induced changes to the structure of two network-forming silicate glasses containing the modifiers Mg and Ca. The materials are important in both commercial display glass and the Earth's lower crust and mantle. We trace the changes that take place to both the network structures and the coordination environments of Mg and Ca. The results show that the pressure-induced growth in the Mg-O and Ca-O coordination numbers originates from an increased number of connections to bridging oxygen atoms in the silicate network. The results also show that three-fold coordinated oxygen atoms are rare.
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Why is it important?
The glasses are model materials for investigating the effect of pressure on more complex materials that are of both commercial and geophysical interest. For example, in the design of resilient glass for e.g. mobile electronic devices, it is important to know the structure of glass under pressure in order to understand the processes that take place when a glass surface is scratched or indented. The investigated materials are also structural proxies for silicate melts. So, the results offer structural insight into why the measured viscosity decreases with increasing pressure.
Perspectives
The neutron diffraction work provides experimental data to test the efficacy of the theoretical schemes used in molecular dynamics modelling. In turn, the models provide information on the structure and dynamics that goes will beyond that available from experiment. When combined, accurate information is gained on the properties of important amorphous materials under high pressure conditions.
Professor Philip S Salmon
University of Bath
Read the Original
This page is a summary of: Pressure induced structural transformations in amorphous MgSiO3 and CaSiO3, Journal of Non-Crystalline Solids X, May 2019, Elsevier,
DOI: 10.1016/j.nocx.2019.100024.
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