First principles prediction of a new high‐pressure phase of dense hydrous magnesium silicates in the lower mantle. Issue 17 (4th September 2013)

• Record Type: Journal Article
• Authors: Tsuchiya, Jun
• Is Part Of: Geophysical research letters. Volume 40:Issue 17(2013:Sep.)
• Page Start: 4570
• Page End: 4573
• Publication Date: 2013-09-04
• Subjects: Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/grl.50875
• Languages: English
• ISSNs: 0094-8276

Abstract

<abstract abstract-type="main" id="grl50875-abs-0001"> <title> <x xml:space="preserve">Abstract</x> </title> <p id="grl50875-para-0001">[1] First principles calculations have shown that the high‐pressure phase transition of phase D MgSi₂<italic>O</italic>₆<italic>H</italic>₂ to the new high‐pressure hydrous phase MgSiO₄<italic>H</italic>₂ plus stishovite occurs at about 40 GPa. The crystal structure of the new phase is very similar to that of CaCl₂‐type SiO₂ and has monoclinic symmetry with space group <italic>P2/m</italic>. This new hydrous phase is stable up to about 52 GPa and then dissociates into MgSiO₃ perovskite and H₂O (ice VIII) at static 0 K conditions. The Clapeyron slope between phase D and the new phase + SiO₂ is positive; about 6.4 MPa/K at 1000 K. This new hydrous phase further extends the stability field of dense hydrous magnesium silicates and also opens the pathway toward the existence of a high‐pressure phase of ice at the lower mantle conditions.</p> </abstract>