Figure 2. Angle dispersive synchrotron X-ray diffraction data for C₆N₉H₃·HCl obtained up to P = 70 GPa (λ_o = 0.4441 Å).

Peaks of interest are labelled with hkl designations according to the P6₃/m space group. (a) Selected patterns showing the onset of peak broadening for the layered phase above 10 GPa followed by the rapid emergence of the new pattern above 40 GPa. (b) Variation of d spacings measured for the principal peak maxima assigned to the low pressure graphitic phase as a function of pressure.