The crystal structure of the high-pressure phase of hexahydro-1,3,5-trinitro-1,3,5-triazine (
![](/images/gifchars/gamma.gif)
-RDX), which isstable above 4 GPa at room temperature, was investigated by using infrared spectroscopy and powder X-raydiffraction measurements followed by Rietveld refinements using a diamond anvil cell (DAC). Although
![](/images/gifchars/gamma.gif)
and
![](/images/gifchars/alpha.gif)
phases were found to belong to the same space group
Pbca, they exhibited a different crystal packing.The molecular structure of the
![](/images/gifchars/gamma.gif)
phase exhibited the same conformation as that of the
![](/images/gifchars/alpha.gif)
phase; however, thetorsion angles of N-NO
2 changed marginally.