Formation of triclusters in silica melt under high pressure

S Hayafune and T Sakamaki and H Ichikawa and Y Onodera and S Kohara and A Suzuki, JOURNAL OF THE CERAMIC SOCIETY OF JAPAN, 133, 242-245 (2025).

DOI: 10.2109/jcersj2.25042

Silica (SiO2) is the major glass-forming material, and the structures of silica glass and melt have been extensively studied using X-ray and neutron diffraction techniques. The diffraction data of silica glass and melt show the first sharp diffraction peak (FSDP) at Q 3 1.5 -1, which is a signature of intermediate-range order. In this study, we performed classical molecular dynamics (MD) simulations at 2000 K and 5 GPa to understand the behaviour of the diffraction peak associated with the modification of intermediate-range order. The highpressure melt data obtained show the decrease in the height of FSDP with a shift of the peak position to the highQ side in X-ray diffraction data, although the average coordination number of four was maintained. In addition, we observed the formation of OSi3 triclusters, which share an oxygen atom with a SiO4 tetrahedron. This unusually dense packed atomic arrangement is the result of high pressure and is associated with the very sharp principal peak observed at Q 3 3 -1 in the O-O partial structure factor derived by MD simulation.

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