Anomalous elastic properties in stishovite

Auxetics are materials which have a negative Poisson's ratio, that is, upon uniaxial tensile loading, they also expand in a direction perpendicular to the applied force. Here, we analyze the elastic constants of stishovite, a high pressure silica polymorph which is known to be a significant con...

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Bibliographic Details
Published in:RSC advances 2015, Vol.5 (12), p.8974-8980
Main Authors: Azzopardi, K. M., Brincat, J. P., Grima, J. N., Gatt, Ruben
Format: Article
Language:English
Subjects:
Constituents
Distortion
Earth mantle
Elastic constants
Oxides
Planes
Poissons ratio
Stishovite
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Summary:Auxetics are materials which have a negative Poisson's ratio, that is, upon uniaxial tensile loading, they also expand in a direction perpendicular to the applied force. Here, we analyze the elastic constants of stishovite, a high pressure silica polymorph which is known to be a significant constituent of the earth's mantle, and show that it exhibits a negative Poisson's ratio when stressed in a range of directions in the (100), (010) and (001) planes under specific ambient pressure ranges. We explain this behaviour through mechanisms involving rotations and distortions of the constituent octahedra. These findings have important practical implications since stishovite is one of the hardest known oxides, and has proven to be important to various fields ranging from seismology to materials science.
ISSN:2046-2069
2046-2069
DOI:10.1039/C4RA12072H