Physics
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufm.p32a..03t&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #P32A-03
Physics
[1027] Geochemistry / Composition Of The Planets, [3924] Mineral Physics / High-Pressure Behavior, [6296] Planetary Sciences: Solar System Objects / Extra-Solar Planets, [8147] Tectonophysics / Planetary Interiors
Scientific paper
Currently, the interior of terrestrial exoplanets (i.e. super-Earths) is highly unclear. In this study, we performed a structural search by means of ab initio quantum mechanical simulation techniques, which we have applied successfully in several studies (e.g. Tsuchiya et al. 2004ab; Tsuchiya et al., 2005; Tsuchiya and Tsuchiya, 2006; Tsuchiya et al., 2008; Tsuchiya and Tsuchiya, 2008; Yusa et al., 2009), to establish ultrahigh-pressure (P) and temperature (T) phase relationships of major Earth mantle matters and to try to make a standard internal structure model of super-Earths. It has been known that silica (SiO2) shows a sequential phase evolution from quartz, coesite, stishovite, CaCl2, α-PbO2 and pyrite (modified fluorite) with elevating pressure (e.g., Teter et al., 1998; Tsuchiya et al., 2004a; Kuwayama et al., 2005). However, further denser phases are still underdetermined, although studies on some low-pressure analogs have suggested an orthorhombic cotunnite phase as the final high-pressure phase (e.g. Haines et al., 1997; Dubrovinskaia et al., 2001; Haines et al., 2001). After examining several dense structure types with AX2 compound, we successfully discovered a new phase transformation of pyrite type SiO2 at multi-megabar condition to an unexpected hexagonal Fe2P structure, which possesses quite high nine-fold coordinated Si and eclipses the cotunnite stability field in the entire pressure range up to 2000 GPa. We subsequently investigated high-pressure stabilities of some important silicate compounds (MgSiO3 and CaSiO3) and found that the new phase change in silica could initiate breakdown of these silicates to oxide mixtures in the conditions relevant to the interior of massive super-Earths and exoplanets, which would lead to various complexities in their internal structures. Our calculations show that relatively large density jump is associated with the breakdown of MgSiO3 post-perovskite to Fe2P-SiO2 plus B2-MgO, while the breakdown of CaSiO3 yields an oxide but metallic phase. These might have substantial effects on the structure and dynamics of giant terrestrial planets, which will be discussed in the presentation. Research supported by JSPS Grant-in-Aid for Scientific Research Grants 20001005 and 21740379 and the Ehime Univ G-COE program "Deep Earth Mineralogy". Dubrovinskaia et al. (2001) Phys. Rev. Lett. 87, 275501. Haines et al. (1997) J. Am. Ceram. Soc. 80, 1910. Haines et al. (2001) Phys. Rev. B 64, 134110. Kuwayama et al. (2005) Science 309, 923. Teter et al. (1998) Phys. Rev. Lett. 80, 2145. Tsuchiya et al. (2004a) Geophys. Res. Lett. 31, L11610. Tsuchiya et al. (2004b) Earth Planet. Sci. Lett. 224, 241. Tsuchiya et al. (2005) Phys. Rev. B 72, 020103(R). Tsuchiya and Tsuchiya (2006) Am. Mineral. 91, 1879. Tsuchiya et al. (2008) J. Miner. Petrol. Sci. 103, 116. Tsuchiya and Tsuchiya (2008) PNAS 105, 19160. Yusa et al. (2009) Inorg. Chem. 48, 7537.
Tsuchiya Jun
Tsuchiya Takuya
No associations
LandOfFree
A Novel Dense Phase of Silica Initiating Silicates Breakdown in Giant Terrestrial Planets (Invited) does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with A Novel Dense Phase of Silica Initiating Silicates Breakdown in Giant Terrestrial Planets (Invited), we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A Novel Dense Phase of Silica Initiating Silicates Breakdown in Giant Terrestrial Planets (Invited) will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1496687