Structural and chemical modifications of carbon dioxide on transport to the deep earth

The structural and chemical changes to which carbon dioxide is subjected with increasing pressure and temperature are discussed here with the purpose of following the modifications of this important geochemical material on proceeding from the Earth's surface down to the core-mantle boundary. The relevance of metasta-bilities, and then of kinetic controlled transformations, is evidenced in the P-T ranges characteristic of both molecular phases and extended covalently bonded structures. From a chemical point of view, this analysis high-lights how the characterization of the melting of the extended structures would represent an important step to understand the role of this compound in the chemistry of the Earth's mantle.