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Title: Transformation of shock-compressed graphite to hexagonal diamond in nanoseconds

The graphite-to-diamond transformation under shock compression has been of broad scientific interest since 1961. The formation of hexagonal diamond (HD) is of particular interest because it is expected to be harder than cubic diamond and due to its use in terrestrial sciences as a marker at meteorite impact sites. However, the formation of diamond having a fully hexagonal structure continues to be questioned and remains unresolved. Using real-time (nanosecond), in situ x-ray diffraction measurements, we show unequivocally that highly oriented pyrolytic graphite, shock-compressed along the c axis to 50 GPa, transforms to highly oriented elastically strained HD with the (100)HD plane parallel to the graphite basal plane. These findings contradict recent molecular dynamics simulation results for the shock-induced graphite-to-diamond transformation and provide a benchmark for future theoretical simulations. Additionally, our results show that an earlier report of HD forming only above 170 GPa for shocked pyrolytic graphite may lead to incorrect interpretations of meteorite impact events.
Authors:
ORCiD logo [1] ; ORCiD logo [1] ;  [2] ; ORCiD logo [1] ; ORCiD logo [2]
  1. Washington State Univ., Pullman, WA (United States). Inst. for Shock Physics
  2. Washington State Univ., Pullman, WA (United States). Inst. for Shock Physics; Washington State Univ., Pullman, WA (United States). Dept. of Physics and Astronomy
Publication Date:
Grant/Contract Number:
NA0002442; NA0002007; AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Science Advances
Additional Journal Information:
Journal Volume: 3; Journal Issue: 10; Journal ID: ISSN 2375-2548
Publisher:
AAAS
Research Org:
Washington State Univ., Pullman, WA (United States). Inst. for Shock Physics
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA), Office of Defense Programs (DP) (NA-10)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE
OSTI Identifier:
1410678
Alternate Identifier(s):
OSTI ID: 1410676