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Ultrahigh‐Pressure Phase Transitions in FeS 2 and FeO 2 : Implications for Super‐Earths' Deep Interior
Author(s) -
Huang Shengxuan,
Wu Xiang,
Qin Shan
Publication year - 2018
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2017jb014766
Subject(s) - iron sulfide , planet , mantle (geology) , density functional theory , high pressure , structural stability , sulfide , phase transition , materials science , chemistry , thermodynamics , physics , geophysics , metallurgy , sulfur , computational chemistry , astrophysics , engineering , structural engineering
Iron oxides play an important role in planetary evolution, but little information about the structural properties of AX 2 ‐type iron oxides under extreme conditions limits our understanding of the so‐called “super‐Earth” planets. Here an investigation into the high‐pressure behavior of FeO 2 as well as its sulfide counterpart FeS 2 , has been conducted by first‐principle calculations based on density functional theory. Both FeO 2 and FeS 2 are predicted to undergo a Pa 3 ¯ ‐ R 3 ¯ m ‐ I 4/ mmm transition sequence at extreme pressure. Differences in high‐pressure behaviors between FeO 2 and FeS 2 have been discussed in detail, such as effective coordination number and elasticity. This study not only resolves the controversy about the structural stability of FeS 2 under high pressure but also suggests the tenfold coordinated I 4/ mmm ‐type FeO 2 may contribute to local chemical heterogeneity by accumulation in the deep interior of a large super‐Earth or water‐rich planet, whose pressure at the core‐mantle boundary can reach 2 TPa.