Figure 6. Powder-diffraction pattern of seifertite.

X-ray data collected at Rigaku diffractometer with MoKα radiation of the sample recovered after compression to about 50 GPa of the powder of α-cristobalite (red line in the middle). For comparison, we provide diffraction patterns of the material obtained by Prokopenko et al.¹² by compression–decompression of starting cristobalite sample to ∼50 GPa at ambient temperature and without pressure-transmitting medium and then quenched to ambient conditions α-PbO₂ structure (blue lower curve), as well as quenched seifertite synthesized at high PT conditions (grey upper curve, Grocholski et al.²³). The similarity in the diffraction patterns is obvious.