Synthesis of carbon doped niccolite phase of SiO2 under geothermal conditions

Despite the paramount importance of the chemical relationship between CO2 and SiO2, their reactivity and their importance for the deep earth oxide chemistry and carbon cycle have not been deeply explored under pressures at pressure-temperature conditions relevant to the Earth’s lowermost mantle.
We have recently (CH-6636, ESRF) obtained evidence of the formation of the niccolite phase of SiO2 by laser heating a thin SiO2 plate immersed into a CO2 pressure medium at pressures and temperatures (85 GPa and 2000-3000 K) where this phase is unstable based on the literature. Its stability on the T quenched material at 100 GPa could be due to the carbon incorporation in the tetrahedral sites of the half occupied oxygen sublattice of the SiO2 niccolite phase.
Due to the great importance of this potential discovery, we propose here to continue this investigation to confirm the synthesis of the niccolite phase, eventually providing its stability range and an the equation of state.