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

• Published in: Nature communications Vol. 5; no. 1; p. 5447
• Main Authors: Németh, Péter, Garvie, Laurence A. J., Aoki, Toshihiro, Dubrovinskaia, Natalia, Dubrovinsky, Leonid, Buseck, Peter R.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 20.11.2014; Nature Publishing Group
• Subjects: 639/301; 639/33/445/330; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms6447

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. Lonsdaleite has been used as a marker of asteroid impacts and is thought to have mechanical properties superior to diamond; however, pure lonsdaleite has not been described or fabricated. Here, the authors show that it does not exist as a discrete material and is in fact faulted and twinned cubic diamond.