First-principles prediction of hydrogen partitioning between the core
and mantle
*Atsuroh Ohba1, Taku Tsuchiya1
1. Ehime University Geodynamics Research Center 
Some recent studies have reported high-P,T hydrous minerals which are stable at the core mantle
boundary (CMB) pressure (Sano et al., 2008; Ohhira et al., 2016; Nishi et al., 2017). In order to elucidate
the water circulation in the Earth's interior, experiments on the reaction between iron and hydrous
minerals or water were also conducted (Iizuka-Oku et al., 2016; Mao et al., 2018; Clesi et al., 2018).
However, the partition of hydrogen reported is different in different studies. In this study, we try estimating
hydrogen partitioning between molten silicate and liquid iron under the CMB conditions based on the
first principles calculation method combined with thermodynamic integration similar to our previous
study (Xiong et al., 2018). Here, we assume following the exchange reaction of water between liquid iron
and molten silicate is expressed as follows 
(16MgSiO3+H2O) + 50Fe ⇔16MgSiO3 + (50Fe+H2O) 
as a first example with ensuring the charge neutrality. Here, reaction free energy is calculated by the
thermodynamic integration molecular dynamics method (Taniuchi & Tsuchiya, 2018). In the moment,
simulations suggest that water prefer liquid iron. Now, additional computations are ongoing for improving
numerical accuracy. The mechanism dissolving water into liquid iron is also investigated.  
SIT21-P18Japan Geoscience Union Meeting 2019
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