Stability and properties of liquid CO₂ at high pressure and high temperature: Implications for electrical conductivities in Earth's lower mantle

Abstract

Carbon dioxide (CO2), one of the most important planetary materials, has been the subject of extensive experimental and theoretical studies. However, the stabilities and properties of CO2 at high pressures and temperatures relevant to Earth's mantle and core remain controversial. We have studied the molten structures of CO2‐V with first‐principles molecular dynamic calculations at 60 GPa and different temperatures. The formation of oxygen molecules in the melt is consistent with experimental observations. In particular, the melting transition is accompanying by metallization. The metallic behavior is shown to originate from electron delocalization between oxygen via the overlap of the π orbitals from the dissociated oxygen‐rich species. Metallic molten CO2 is a potential candidate to explain the high conductivities of the Earth's lower mantle. Furthermore, theoretical results do not support the existence of the proposed ionic solid phase of CO2 at high temperature and high pressure.

Structures and Transport Properties of CaCO3 Melts under Earth’s Mantle Conditions

“…Multiple lines of evidence from inclusions in superdeep diamond, high P-T melting experiments and theoretical calculations suggest that carbonatitic melts are present down to the lower mantle. − Therefore, knowledge about the structures and properties of carbonatitic melts under pressure not only has significant impact on the geological processes research from mantle geodynamics to volcanic activities but also important for the understanding of the related deep carbon cycle and global climate change. − …”