Prediction of novel stable compounds in the Mg-Si-O system under exoplanet pressures
The Mg-Si-O system is the major Earth and rocky planet-forming system. Here, through quantum variable-composition evolutionary structure explorations, we have discovered several unexpected stable binary and ternary compounds in the Mg-Si-O system. Besides the well-known SiO 2 phases, we have found t...
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Veröffentlicht in: | Scientific reports 2015-12, Vol.5 (1), p.18347-18347, Article 18347 |
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Sprache: | eng |
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Zusammenfassung: | The Mg-Si-O system is the major Earth and rocky planet-forming system. Here, through quantum variable-composition evolutionary structure explorations, we have discovered several unexpected stable binary and ternary compounds in the Mg-Si-O system. Besides the well-known SiO
2
phases, we have found two extraordinary silicon oxides, SiO
3
and SiO, which become stable at pressures above 0.51 TPa and 1.89 TPa, respectively. In the Mg-O system, we have found one new compound, MgO
3
, which becomes stable at 0.89 TPa. We find that not only the (MgO)
x
·(SiO
2
)
y
compounds, but also two (MgO
3
)
x
·(SiO
3
)
y
compounds, MgSi
3
O
12
and MgSiO
6
, have stability fields above 2.41 TPa and 2.95 TPa, respectively. The highly oxidized MgSi
3
O
12
can form in deep mantles of mega-Earths with masses above 20 M
⊕
(M
⊕
:Earth’s mass). Furthermore, the dissociation pathways of pPv-MgSiO
3
are also clarified and found to be different at low and high temperatures. The low-temperature pathway is MgSiO
3
⇒ Mg
2
SiO
4
+ MgSi
2
O
5
⇒ SiO
2
+ Mg
2
SiO
4
⇒ MgO + SiO
2
, while the high-temperature pathway is MgSiO
3
⇒ Mg
2
SiO
4
+ MgSi
2
O
5
⇒ MgO + MgSi
2
O
5
⇒ MgO + SiO
2
. Present results are relevant for models of the internal structure of giant exoplanets and for understanding the high-pressure behavior of materials. |
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ISSN: | 2045-2322 2045-2322 |
DOI: | 10.1038/srep18347 |