| Autor: |
Németh P; 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., Garvie LA; 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., Aoki T; LeRoy Eyring Center for Solid State Science, Arizona State University, Tempe, Arizona 85287-1704, USA., Dubrovinskaia N; Material Physics and Technology at Extreme Conditions, Laboratory of Crystallography, University of Bayreuth, Bayreuth D-95440, Germany., Dubrovinsky L; Bayerisches Geoinstitut, Universität Bayreuth, Bayreuth D-95440, Germany., Buseck PR; 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. |
| Abstrakt: |
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. |
