Transformation of graphite to diamond via a topotactic mechanism

Laurence Garvie; Péter Németh; P R Buseck

doi:10.1515/am.2014.4658

Transformation of graphite to diamond via a topotactic mechanism

Laurence Garvie, Péter Németh, P R Buseck

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30 Scopus citations

Abstract

Several mechanisms and intermediate steps have been proposed to explain the transformation of graphite to diamond. However, the mechanism continues to be debated, in part because graphite that is incompletely transformed to diamond has not been reported; although such material could be used to better understand the diamond-forming process. Here we report the discovery of nano-sized grains of interstratified graphite and diamond from Gujba, an extraterrestrially shocked meteorite. We use high-resolution transmission electron microscopy (HRTEM) data from these grains to show that diamond formed via a reconstructive, topotactic rather than martensitic mechanism. Electron diffraction and HRTEM images show the following three-dimensional crystallographic relationships between the interstratified graphite and diamond: (001)_g||(111) _d, (100)_g||(211)_d, and (120) _g||(011)_d. These relationships yield the transition matrix linking the graphite and diamond unit cells, which become coincident for graphite compressed to 7 GPa. The specific product, whether single-crystal or twinned diamond, is dictated by the initial graphite polytype and transformation route. The derivation of a three-dimensional transition matrix is consistent with a topotactic relationship between graphite and the newly formed diamond.

Original language	English (US)
Pages (from-to)	531-538
Number of pages	8
Journal	American Mineralogist
Volume	99
Issue number	2-3
DOIs	https://doi.org/10.1515/am.2014.4658
State	Published - Feb 2014

Keywords

Crystal structure
crystal growth
electron microscopy
meteorite

ASJC Scopus subject areas

Geophysics
Geochemistry and Petrology

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10.1515/am.2014.4658

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title = "Transformation of graphite to diamond via a topotactic mechanism",

abstract = "Several mechanisms and intermediate steps have been proposed to explain the transformation of graphite to diamond. However, the mechanism continues to be debated, in part because graphite that is incompletely transformed to diamond has not been reported; although such material could be used to better understand the diamond-forming process. Here we report the discovery of nano-sized grains of interstratified graphite and diamond from Gujba, an extraterrestrially shocked meteorite. We use high-resolution transmission electron microscopy (HRTEM) data from these grains to show that diamond formed via a reconstructive, topotactic rather than martensitic mechanism. Electron diffraction and HRTEM images show the following three-dimensional crystallographic relationships between the interstratified graphite and diamond: (001)g||(111) d, (100)g||(211)d, and (120) g||(011)d. These relationships yield the transition matrix linking the graphite and diamond unit cells, which become coincident for graphite compressed to 7 GPa. The specific product, whether single-crystal or twinned diamond, is dictated by the initial graphite polytype and transformation route. The derivation of a three-dimensional transition matrix is consistent with a topotactic relationship between graphite and the newly formed diamond.",

keywords = "Crystal structure, crystal growth, electron microscopy, meteorite",

author = "Laurence Garvie and P{\'e}ter N{\'e}meth and Buseck, {P R}",

note = "Funding Information: We are grateful to the staff and for use of the facilities in the John M. Cowley Center for High Resolution Electron Microscopy at Arizona State University. L.A.J.G was supported by NASA Origins of Solar Systems grant NNX11AK58G and P.N. acknowledges support from Hungarian Scientific Research Fund and Hungarian Economic Development Centre grant HUMAN_MB08-1-2011-0012. The work at ASU was also supported by Cosmochemistry grant NNX10AG48G. The authors are grateful to the associate editor Ian Swainson, and the three reviewers (A. El Goresey and two anonymous), for their insightful comments and suggestions.",

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doi = "10.1515/am.2014.4658",

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AU - Garvie, Laurence

AU - Németh, Péter

AU - Buseck, P R

N1 - Funding Information: We are grateful to the staff and for use of the facilities in the John M. Cowley Center for High Resolution Electron Microscopy at Arizona State University. L.A.J.G was supported by NASA Origins of Solar Systems grant NNX11AK58G and P.N. acknowledges support from Hungarian Scientific Research Fund and Hungarian Economic Development Centre grant HUMAN_MB08-1-2011-0012. The work at ASU was also supported by Cosmochemistry grant NNX10AG48G. The authors are grateful to the associate editor Ian Swainson, and the three reviewers (A. El Goresey and two anonymous), for their insightful comments and suggestions.

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N2 - Several mechanisms and intermediate steps have been proposed to explain the transformation of graphite to diamond. However, the mechanism continues to be debated, in part because graphite that is incompletely transformed to diamond has not been reported; although such material could be used to better understand the diamond-forming process. Here we report the discovery of nano-sized grains of interstratified graphite and diamond from Gujba, an extraterrestrially shocked meteorite. We use high-resolution transmission electron microscopy (HRTEM) data from these grains to show that diamond formed via a reconstructive, topotactic rather than martensitic mechanism. Electron diffraction and HRTEM images show the following three-dimensional crystallographic relationships between the interstratified graphite and diamond: (001)g||(111) d, (100)g||(211)d, and (120) g||(011)d. These relationships yield the transition matrix linking the graphite and diamond unit cells, which become coincident for graphite compressed to 7 GPa. The specific product, whether single-crystal or twinned diamond, is dictated by the initial graphite polytype and transformation route. The derivation of a three-dimensional transition matrix is consistent with a topotactic relationship between graphite and the newly formed diamond.

AB - Several mechanisms and intermediate steps have been proposed to explain the transformation of graphite to diamond. However, the mechanism continues to be debated, in part because graphite that is incompletely transformed to diamond has not been reported; although such material could be used to better understand the diamond-forming process. Here we report the discovery of nano-sized grains of interstratified graphite and diamond from Gujba, an extraterrestrially shocked meteorite. We use high-resolution transmission electron microscopy (HRTEM) data from these grains to show that diamond formed via a reconstructive, topotactic rather than martensitic mechanism. Electron diffraction and HRTEM images show the following three-dimensional crystallographic relationships between the interstratified graphite and diamond: (001)g||(111) d, (100)g||(211)d, and (120) g||(011)d. These relationships yield the transition matrix linking the graphite and diamond unit cells, which become coincident for graphite compressed to 7 GPa. The specific product, whether single-crystal or twinned diamond, is dictated by the initial graphite polytype and transformation route. The derivation of a three-dimensional transition matrix is consistent with a topotactic relationship between graphite and the newly formed diamond.

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Transformation of graphite to diamond via a topotactic mechanism

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Keywords

ASJC Scopus subject areas

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