Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 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 SiO2 phases, we have found two
extraordinary silicon oxides, SiO3 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, MgO3, which becomes stable at 0.89 TPa. We find that not only
the (MgO)x(SiO2)y compounds, but also two (MgO3)x(SiO3)y compounds, MgSi3O12
and MgSiO6, have stability fields above 2.41 TPa and 2.95 TPa, respectively.
The highly oxidized MgSi3O12 can form in deep mantles of mega-Earths with
masses above 20 M+ (M+:Earth's mass). Furthermore, the dissociation pathways of
pPv-MgSiO3 are also clarified, and found to be different at low and high
temperatures. The low-temperature pathway is MgSiO3 -> Mg2SiO4 + MgSi2O5 ->
SiO2 + Mg2SiO4 -> MgO + SiO2, while the high-temperature pathway is MgSiO3 ->
Mg2SiO4 + MgSi2O5 -> MgO + MgSi2O5 -> MgO + SiO2. 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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The categories of this paper are: acc-phys
13
The categories of this paper are: quant-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: adap-org
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The categories of this paper are: q-fin
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The categories of this paper are: eess
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The categories of this paper are: stat
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-ex
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The categories of this paper are: patt-sol
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The categories of this paper are: cmp-lg
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The categories of this paper are: atom-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: plasm-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: q-bio