Abstract:
:We present ab initio calculations of the phase diagram of liquid CO(2) and its melting curve over a wide range of pressure and temperature conditions, including those relevant to the Earth. Several distinct liquid phases are predicted up to 200 GPa and 10,000 K based on their structural and electronic characteristics. We provide evidence for a first-order liquid-liquid phase transition with a critical point near 48 GPa and 3,200 K that intersects the mantle geotherm; a liquid-liquid-solid triple point is predicted near 45 GPa and 1,850 K. Unlike known first-order transitions between thermodynamically stable liquids, the coexistence of molecular and polymeric CO(2) phases predicted here is not accompanied by metallization. The absence of an electrical anomaly would be unique among known liquid-liquid transitions. Furthermore, the previously suggested phase separation of CO(2) into its constituent elements at lower mantle conditions is examined by evaluating their Gibbs free energies. We find that liquid CO(2) does not decompose into carbon and oxygen up to at least 200 GPa and 10,000 K.
journal_name
Proc Natl Acad Sci U S Aauthors
Boates B,Teweldeberhan AM,Bonev SAdoi
10.1073/pnas.1120243109subject
Has Abstractpub_date
2012-09-11 00:00:00pages
14808-12issue
37eissn
0027-8424issn
1091-6490pii
1120243109journal_volume
109pub_type
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