Figure 5: (a) Evolution of the diffraction patterns
of and ionic solids on decompression at 500 K. The transformation of the phase mixture
to pure is confirmed by
the Rietveld refinement (b) of the hexagonal structural model () of at 8.2 GPa and 500 K. The refined lattice parameters
are ; . The , , and fractional atomic coordinates for two nitrogen and
two oxygen atoms in asymmetric unit are ; ; ; .