High Pressure Crystallography Of Hexanitrohexaazaisowurtzitane On A SMART CCD Diffractometer. M. J. Hardie, K. Kirschbaum, A. Martin, A. A. Pinkerton and R. Tanbug, Department of Chemistry, University of Toledo, Toledo, Ohio 43606, T. P. Russell, Naval Research Laboratory, Washington DC, 20375 and G. J. Piermarini, National Institute of Standards and Technology, Gaithersburg, MD 20899.

A new high pressure diamond anvil cell has been used for single crystal diffraction studies of large organic molecules at high pressure on a Siemens Platform Diffractometer using a CCD detector. The cell can be used for static pressures up to 5.0 GPa and incorporates boron carbide spheres instead of the more usual beryllium plates.

Preliminary studies of a single crystal of [gamma]-hexanitrohexaazaisowurtzitane (HNIW) have given monoclinic unit cell parameters a = 13.2277(3), b = 8.1666(2), c = 14.8810(5) Å, [beta] = 109.150(2)deg..

[gamma]-HNIW is known to undergo a phase transition to the high pressure [zeta]-HNIW phase at 0.7 GPa. Structural parameters for HNIW at a variety of pressures, estimated by ruby fluorescence, will be presented.