Coesite-like CO2: An analog to SiO2

We report recent findings of coesite-like carbon dioxide phases: coesite I phase (cI-CO2) formed by laser-heating pseudo-six-fold phase VI above 50 GPa, a high-pressure form of coesite (cII-CO2) by further compressing cI phase above 70 GPa, and an amorphous form above 100 GPa. The existence of coesite-like carbon dioxide, an important linkage between fourfold quartz and sixfold stishovite in SiO2, underscores the periodic analogy between SiO2 and CO2, which has been in a recent controversy. Its pressure-temperature stability field signifies the possibility of volatile CO2 incorporated in silicate minerals in the Earth's lower mantle.