Fig. 2: Raman spectra and X-ray diffraction pattern of CaOx.
From: Pressure-stabilized divalent ozonide CaO3 and its impact on Earth’s oxygen cycles
a Raman spectra of Ca–O compounds at high pressure. The calculated frequencies of Raman active vibrational modes are indicated by vertical bars. b Measured powder X-ray diffraction pattern of Ca–O compounds at 35 GPa with the Rietveld method (XRD 2D image is shown at the top; inset shows a microphotographic image in the gasket hole of about 100 μm through diamond culets). Vertical ticks correspond to the Bragg peaks of CaO3 (pink), CaO4 (orange), CaO (purple), and solid O2 (wine). The X-ray wavelength is 0.4337 Å. The obtained lattice pentameters are a = 4.11 Å, c = 5.04 Å for tetragonal CaO4, a = 4.49 Å for cubic CaO, and a = 7.13 Å, b = 4.57 Å, c = 3.74 Å, β = 110.2° for monoclinic oxygen.
