title: Lonsdaleite is faulted and twinned cubic diamond and does not exist as a discrete material.
abstract: 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.
authors.affiliation: 1] Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest 1117, Hungary [2] Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, USA.
authors.forename: Péter
authors.initials: P
authors.lastname: Németh
authors.affiliation: 1] Center for Meteorite Studies, Arizona State University, Tempe, Arizona 85287-6004, USA [2] School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, USA.
authors.forename: Laurence A J
authors.initials: LA
authors.lastname: Garvie
authors.affiliation: LeRoy Eyring Center for Solid State Science, Arizona State University, Tempe, Arizona 85287-1704, USA.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Aoki
authors.affiliation: Material Physics and Technology at Extreme Conditions, Laboratory of Crystallography, University of Bayreuth, Bayreuth D-95440, Germany.
authors.forename: Natalia
authors.initials: N
authors.lastname: Dubrovinskaia
authors.affiliation: Bayerisches Geoinstitut, Universität Bayreuth, Bayreuth D-95440, Germany.
authors.forename: Leonid
authors.initials: L
authors.lastname: Dubrovinsky
authors.affiliation: 1] School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, USA [2] Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, USA.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Buseck