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Title: Thermal evolution of the metastable r8 and bc8 polymorphs of silicon

The kinetics of two metastable polymorphs of silicon under thermal annealing was investigated. These phases with body-centered cubic bc8 and rhombohedral r8 structures can be formed upon pressure release from metallic silicon.We study these metastable polymorphs were formed by two different methods, via point loading and in a diamond anvil cell (DAC). Upon thermal annealing different transition pathways were detected. In the point loading case, the previously reported Si-XIII formed and was confirmed as a new phase with an as-yet-unidentified structure. In the DAC case, bc8-Si transformed to the hexagonal-diamond structure at elevated pressure, consistent with previous studies at ambient pressure. In contrast, r8-Si transformed directly to diamond-cubic Si at a temperature of 255⁰C. In conclusion, these data were used to construct diagrams of the metastability regimes of the polymorphs formed in a DAC and may prove useful for potential technological applications of these metastable polymorphs.
 [1] ;  [2] ;  [3] ;  [3] ;  [1] ;  [1]
  1. Australian National Univ., Canberra, ACT (Australia)
  2. Carnegie Inst. of Science, Washington, DC (United States)
  3. Carnegie Inst. of Washington, Argonne, IL (United States). Geophysical Lab.
Publication Date:
OSTI Identifier:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
High Pressure Research
Additional Journal Information:
Journal Volume: 35; Journal Issue: 2; Journal ID: ISSN 0895-7959
Taylor & Francis
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
36 MATERIALS SCIENCE; pressure-induced transitions; metastable polymorphs; silicon; in situ annealing