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Molecular dynamics study of liquid silica under high pressure

Takada, A; Bell, RG; Catlow, CRA; (2016) Molecular dynamics study of liquid silica under high pressure. Journal of Non-Crystalline Solids , 451 pp. 124-130. 10.1016/j.jnoncrysol.2016.06.005. Green open access

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Abstract

Structural changes of liquid silica are investigated under high pressure by molecular dynamics simulation. It is well known that high-silica liquids display anomalous pressure-dependent behavior in their diffusivities. The potential model, the so-called ‘soft potential’, is used, as it is expected to simulate the structural changes of silica at high temperature well. With increasing pressure, above the glass transition temperature, the simulated silica melt shows the so-called diffusivity maximum under a pressure of 20 GPa, as already shown by the previous studies. However, it is also found that this diffusivity maximum disappears above 2800 K. The analysis of Si coordination number suggests that the competition between the increase of five-fold and that of three-fold controls the extent of the anomaly. Secondly, the analysis of ‘local oxygen packing number (LOPN)’, that had been developed to investigate geometrical features in amorphous structures, is applied. In a complementary manner to the analysis of the Si coordination number, the local structure in the silica melt shows the gradual structural transformation from a low-density to high density packing on compression. Finally, a model explaining the two types of change of diffusivity in silica melt was proposed in combination with the LOPN analysis and the structon analysis that had been developed to investigate the thermal change of local structures.

Type: Article
Title: Molecular dynamics study of liquid silica under high pressure
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.jnoncrysol.2016.06.005
Publisher version: http://doi.org/10.1016/j.jnoncrysol.2016.06.005
Language: English
Additional information: Copyright © 2017 Elsevier Ltd. All rights reserved. This is an Open Access article made available under a Creative Commons Attribution Non-commercial Non-derivative 4.0 International license (CC BY-NC-ND 4.0). This license allows you to share, copy, distribute and transmit the work for personal and non-commercial use providing author and publisher attribution is clearly stated. Further details about CC BY licenses are available at http://creativecommons.org/ licenses/by/4.0. Access may be initially restricted by the publisher.
Keywords: Silica; Molecular dynamics; Structure; Diffusion
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
URI: https://discovery.ucl.ac.uk/id/eprint/1533206
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