title: Nanosecond formation of diamond and lonsdaleite by shock compression of graphite.
abstract: The shock-induced transition from graphite to diamond has been of great scientific and technological interest since the discovery of microscopic diamonds in remnants of explosively driven graphite. Furthermore, shock synthesis of diamond and lonsdaleite, a speculative hexagonal carbon polymorph with unique hardness, is expected to happen during violent meteor impacts. Here, we show unprecedented in situ X-ray diffraction measurements of diamond formation on nanosecond timescales by shock compression of pyrolytic as well as polycrystalline graphite to pressures from 19 GPa up to 228 GPa. While we observe the transition to diamond starting at 50 GPa for both pyrolytic and polycrystalline graphite, we also record the direct formation of lonsdaleite above 170 GPa for pyrolytic samples only. Our experiment provides new insights into the processes of the shock-induced transition from graphite to diamond and uniquely resolves the dynamics that explain the main natural occurrence of the lonsdaleite crystal structure being close to meteor impact sites.
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720, USA.
authors.forename: D
authors.initials: D
authors.lastname: Kraus
authors.affiliation: SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: A
authors.initials: A
authors.lastname: Ravasio
authors.affiliation: SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: M
authors.initials: M
authors.lastname: Gauthier
authors.affiliation: Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry CV4 7AL, UK.
authors.forename: D O
authors.initials: DO
authors.lastname: Gericke
authors.affiliation: Max-Planck-Institut für Physik Komplexer Systeme, Nöthnitzer Strasse 38, 01187 Dresden, Germany.|Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstrasse 400, 01328 Dresden, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Vorberger
authors.affiliation: Institut für Kernphysik, Technische Universität Darmstadt, Schlossgartenstrasse 9, 64289 Darmstadt, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Frydrych
authors.affiliation: Institut für Kernphysik, Technische Universität Darmstadt, Schlossgartenstrasse 9, 64289 Darmstadt, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Helfrich
authors.affiliation: SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: L B
authors.initials: LB
authors.lastname: Fletcher
authors.affiliation: Institut für Kernphysik, Technische Universität Darmstadt, Schlossgartenstrasse 9, 64289 Darmstadt, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Schaumann
authors.affiliation: SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: B
authors.initials: B
authors.lastname: Nagler
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720, USA.
authors.forename: B
authors.initials: B
authors.lastname: Barbrel
authors.affiliation: Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
authors.forename: B
authors.initials: B
authors.lastname: Bachmann
authors.affiliation: SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: E J
authors.initials: EJ
authors.lastname: Gamboa
authors.affiliation: SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: S
authors.initials: S
authors.lastname: Göde
authors.affiliation: SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: E
authors.initials: E
authors.lastname: Granados
authors.affiliation: Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
authors.forename: G
authors.initials: G
authors.lastname: Gregori
authors.affiliation: SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: H J
authors.initials: HJ
authors.lastname: Lee
authors.affiliation: GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstrasse 1, 64291 Darmstadt, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Neumayer
authors.affiliation: SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: W
authors.initials: W
authors.lastname: Schumaker
authors.affiliation: Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
authors.forename: T
authors.initials: T
authors.lastname: Döppner
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720, USA.
authors.forename: R W
authors.initials: RW
authors.lastname: Falcone
authors.affiliation: SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: S H
authors.initials: SH
authors.lastname: Glenzer
authors.affiliation: Institut für Kernphysik, Technische Universität Darmstadt, Schlossgartenstrasse 9, 64289 Darmstadt, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Roth
mesh_terms: D003460:Crystallization; D018130:Diamond / Q000737:chemistry*; D018534:Earth, Planet; D006108:Graphite / Q000737:chemistry*; D006244:Hardness; D019110:Meteoroids; D008685:Meteorological Concepts; D044367:Phase Transition; D011312:Pressure; D014961:X-Ray Diffraction
chemical_list: D018130:Diamond; D006108:Graphite