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Lonsdaleite is faulted and twinned cubic diamond and does not exist as a discrete material

Description
Lonsdaleite, also called hexagonal diamond, has been widely used as a marker of asteroidal impacts. It is thought to play a central role during the graphite-to-diamond transformation, and calculations suggest that it possesses mechanical properties superior to diamond. However, despite extensive efforts, lonsdaleite has never been produced or described as…

Lonsdaleite, also called hexagonal diamond, has been widely used as a marker of asteroidal impacts. It is thought to play a central role during the graphite-to-diamond transformation, and calculations suggest that it possesses mechanical properties superior to diamond. However, despite extensive efforts, lonsdaleite has never been produced or described as a separate, pure material. Here we show that defects in cubic diamond provide an explanation for the characteristic d-spacings and reflections reported for lonsdaleite. Ultrahigh-resolution electron microscope images demonstrate that samples displaying features attributed to lonsdaleite consist of cubic diamond dominated by extensive {113} twins and {111} stacking faults. These defects give rise to nanometre-scale structural complexity. Our findings question the existence of lonsdaleite and point to the need for re-evaluating the interpretations of many lonsdaleite-related fundamental and applied studies.
ContributorsNemeth, Peter (Author) / Garvie, Laurence (Author) / Aoki, Toshihiro (Author) / Dubrovinskaia, Natalia (Author) / Dubrovinsky, Leonid (Author) / Buseck, Peter (Author) / Department of Chemistry and Biochemistry (Contributor) / College of Liberal Arts and Sciences (Contributor) / School of Earth and Space Exploration (Contributor) / Center for Meteorite Studies (Contributor) / Ira A. Fulton Schools of Engineering (Contributor) / LeRoy Eyring Center for Solid State Science (Contributor) / School of Molecular Sciences (Contributor)
Created2014-11-01