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

• Published in: Geophysical research letters Vol. 42; no. 14; pp. 5820 - 5827
• Main Authors: Wu, Min, Tse, John S., Pan, Yuanming
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 28.07.2015; John Wiley & Sons, Inc
• Subjects: Carbon dioxide; dissociation; Earth; Earth mantle; Electrical resistivity; High pressure; High temperature; Lower mantle; mantle; Mathematical analysis; Melting; metallization; Metallizing; molten structure; Orbitals; Oxygen; Pressure; Properties; Properties (attributes); Stability; Structures; Temperature; Temperature effects; Vanadium
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2015GL064522

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. Key Points Dissociation of carbon dioxide at high pressure and high temperature Metallization of carbon dioxide at high pressure and temperature Molten CO2 may be a contributing factor to the high conductivity of the Earth's mantle