Structure of 1,3,5,7-tetranitro-3,7-diazabicyclo[3.3.0]octane. Structure solution from molecular packing analysis

The structure was solved with the molecular packing program MOLPAK, starting with a molecular mechanics-geometry optimized model of an isolated molecule. The best predicted crystal structures from the MOLPAK procedure were subjected to lattice energy refinement with the WMIN program. The MOLPAK/WMIN-predicted crystal structure, whose cell parameters were closest to the experimental values. gave an initial R of 0.48 for the 173 data to theta = 25 degrees. Four cycles of least-squares refinement of x, y, z and U gave an R of 0.27 for the 277 data to theta = 30 degrees. Final R = 0.038, wR = 0.044. There are no unusual intermolecular distances and crystal packing is normal.