Figure 5. Selected integrated X-ray diffraction patterns collected on heating of FeCO₃ near or above 100 GPa.

Patterns are labelled with the pressure and temperature during data collection. Indices of different phases are coloured as follows: FeCO₃ starting material (black), Ne (magenta), Re (light blue), tetrairon(III) orthocarbonate Fe₄C₃O₁₂ (red) and diiron(II) diiron(III) tetracarbonate Fe₄C₄O₁₃ (green). Neon was used both as a quasi-hydrostatic pressure medium and a pressure standard (Methods section). Data were collected at ID09a at ESRF with an X-ray wavelength of 0.4126 Å.