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Title: Deviatoric stress-induced phase transitions in diamantane

The high-pressure behavior of diamantane was investigated using angle-dispersive synchrotron x-ray diffraction (XRD) and Raman spectroscopy in diamond anvil cells. Our experiments revealed that the structural transitions in diamantane were extremely sensitive to deviatoric stress. Under non-hydrostatic conditions, diamantane underwent a cubic (space group Pa3) to a monoclinic phase transition at below 0.15 GPa, the lowest pressure we were able to measure. Upon further compression to 3.5 GPa, this monoclinic phase transformed into another high-pressure monoclinic phase which persisted to 32 GPa, the highest pressure studied in our experiments. However, under more hydrostatic conditions using silicone oil as a pressure medium, the transition pressure to the first high-pressure monoclinic phase was elevated to 7–10 GPa, which coincided with the hydrostatic limit of silicone oil. In another experiment using helium as a pressure medium, no phase transitions were observed to the highest pressure we reached (13 GPa). In addition, large hysteresis and sluggish transition kinetics were observed upon decompression. Over the pressure range where phase transitions were confirmed by XRD, only continuous changes in the Raman spectra were observed. This suggests that these phase transitions are associated with unit cell distortions and modifications in molecular packing rather than the formation ofmore » new carbon-carbon bonds under pressure.« less
Authors:
;  [1] ; ;  [2] ;  [1] ;  [3] ;  [3]
  1. Geological and Environmental Sciences, Stanford University, Stanford, California 94305 (United States)
  2. Stanford Institute for Materials and Energy Science, Stanford, California 94305 (United States)
  3. (United States)
Publication Date:
OSTI Identifier:
22436605
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 141; Journal Issue: 15; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; COMPRESSION; HELIUM; KINETICS; MONOCLINIC LATTICES; PHASE TRANSFORMATIONS; RAMAN SPECTRA; RAMAN SPECTROSCOPY; SILICONES; SPACE GROUPS; STRESSES; X-RAY DIFFRACTION