The 4th International Conference on Matter and Radiation at Extremes (ICMRE 2019)

487 / 2019-03-18 18:30:09

Novel high-pressure calcium carbonates

carbonate,deep carbon,high pressure chemistry

Plenary track > High Pressure Physics and Materials Science

Calcium and magnesium carbonates are believed to be the host compounds for most of the oxidized carbon in the Earth's mantle. Here, using the evolutionary crystal structure prediction, we systematically explore the MgO-CO2 and CaO-CO2 systems at pressures ranging from 0 to 160 GPa to search for thermodynamically stable magnesium and calcium carbonates. While MgCO3 is the only stable magnesium carbonate, three calcium carbonates are stable under pressure: well-known CaCO3, and previously unknown Ca3CO5 andCaC2O5. Ca3CO5 polymorphs are found to contain isolated orthocarbonate CO4 tetrahedra, and are stable at relatively low pressures (>11 GPa), whereas CaC2O5 is stable above 33 GPa and its polymorphs feature polymeric motifs made of CO4 tetrahedra.