5:15 PM - 6:45 PM
[SIT16-P03] Effects of Si and O in the metal on the S partitioning between liquid metal and molten silicate at high pressure and temperature based on ab initio calculations
Keywords:ab initio calculation, light elements, core-mantle interaction, sulfur, oxygen, silicon
Earth’s core is known to be 5-10% less dense than pure iron, and this density deficit is thought to be due to the incorporation of light elements such as hydrogen, carbon, oxygen, silicon, and sulfur [1]. To constrain the extent to which these light elements are content in the proto-core through core formation processes, it is important to understand their partitioning behavior at high temperatures and pressures.
To investigate the properties of such light elements, we first performed ab initio partitioning calculations of S between liquid iron and molten silicate. The result showed that S has a strong siderophility with a partition coefficient (DS) of ~ 100 at high pressures and temperatures (e.g., 60 GPa, 4000 K) [2]. This suggests that most of S in primitive materials might be absorbed into the core. Here, experimental and theoretical studies [e.g., 2,3] have suggested that the presence of O in liquid iron might change the partitioning behavior of S. However, the effect has been investigated only to a limited extent in partitioning between iron and silicate at high pressure and temperature. Light elements other than O, such as Si, have also not been reported. To further study the sulfur partitioning behavior and to constrain the Earth's core composition, we investigate the effect of O and Si contents in liquid iron on the partitioning of S.
This study investigates the S partitioning between O or Si-bearing liquid iron and molten silicate using ab initio free energy calculations based on the thermodynamic integration method [4,5,6]. The liquid state is simulated by ab initio molecular dynamics simulations based on density functional theory [7,8]. We set up the reaction and composition to reproduce the equilibrium partitioning reaction for S as FeSsilicate+1/2S2↔FeSmetal+1/2O2, often assumed in experimental studies [e.g., 3].
At the moment, our calculations indicate that DS decreases with increasing the O content in liquid iron as these two elements affect exclusively. The behavior of Si is now being calculated.
[1] F. Birch: J. Geophys. Res., 57, 227 (1952). [2] K. Itoh and T. Tsuchiya: JpGU, poster presentation, C001727 (2023). [3] T.A. Suer, et al.: Earth Planet. Sci. Lett., 469, 84 (2017). [4] T. Taniuchi and T. Tsuchiya: J. Phys.: Cond. Matt., 30, 114003 (2018). [5] Z. Xiong, T. Tsuchiya, and T. Taniuchi: J. Geophys. Res.: Solid Earth, 123, 6451 (2018). [6] Z. Xiong, T. Tsuchiya, and J.A. Van Orman: Geophys. Res. Lett., 48, e2020GL090769 (2021). [7] P. Hohenberg and W. Kohn: Phys. Rev., 136, B864 (1964). [8] W. Kohn and L.J. Sham: Phys. Rev., 140, A1133 (1965).
To investigate the properties of such light elements, we first performed ab initio partitioning calculations of S between liquid iron and molten silicate. The result showed that S has a strong siderophility with a partition coefficient (DS) of ~ 100 at high pressures and temperatures (e.g., 60 GPa, 4000 K) [2]. This suggests that most of S in primitive materials might be absorbed into the core. Here, experimental and theoretical studies [e.g., 2,3] have suggested that the presence of O in liquid iron might change the partitioning behavior of S. However, the effect has been investigated only to a limited extent in partitioning between iron and silicate at high pressure and temperature. Light elements other than O, such as Si, have also not been reported. To further study the sulfur partitioning behavior and to constrain the Earth's core composition, we investigate the effect of O and Si contents in liquid iron on the partitioning of S.
This study investigates the S partitioning between O or Si-bearing liquid iron and molten silicate using ab initio free energy calculations based on the thermodynamic integration method [4,5,6]. The liquid state is simulated by ab initio molecular dynamics simulations based on density functional theory [7,8]. We set up the reaction and composition to reproduce the equilibrium partitioning reaction for S as FeSsilicate+1/2S2↔FeSmetal+1/2O2, often assumed in experimental studies [e.g., 3].
At the moment, our calculations indicate that DS decreases with increasing the O content in liquid iron as these two elements affect exclusively. The behavior of Si is now being calculated.
[1] F. Birch: J. Geophys. Res., 57, 227 (1952). [2] K. Itoh and T. Tsuchiya: JpGU, poster presentation, C001727 (2023). [3] T.A. Suer, et al.: Earth Planet. Sci. Lett., 469, 84 (2017). [4] T. Taniuchi and T. Tsuchiya: J. Phys.: Cond. Matt., 30, 114003 (2018). [5] Z. Xiong, T. Tsuchiya, and T. Taniuchi: J. Geophys. Res.: Solid Earth, 123, 6451 (2018). [6] Z. Xiong, T. Tsuchiya, and J.A. Van Orman: Geophys. Res. Lett., 48, e2020GL090769 (2021). [7] P. Hohenberg and W. Kohn: Phys. Rev., 136, B864 (1964). [8] W. Kohn and L.J. Sham: Phys. Rev., 140, A1133 (1965).