Wüstite (FeO), silica (${\mathrm{SiO}}_2$), and water (${\mathrm{H}}_2\mathrm{O}$) are highly abundant in the interior of planets. Given their extensive participation in most geochemical reactions within the mantle of Earth and other planets, it is important to investigate the high-pressure compounds of the ternary $\mathrm{FeO}\text{−}{\mathrm{SiO}}_2\text{−}{\mathrm{H}}_2\mathrm{O}$ system. Here, taking advantage of machine learning assisted crystal structure predictions based on DFT+U calculations, we identified two thermodynamically stable iron hydrosilicate phases, the $\alpha \text{−}{\mathrm{FeSiO}}_4{\mathrm{H}}_2$ and $\beta \text{−}{\mathrm{FeSiO}}_4{\mathrm{H}}_2$ at high pressures of 50–150 GPa and above 150 GPa, respectively. Both these structures exhibit superionic behavior at pressure-temperature conditions corresponding to the Earth's interior. Most importantly, as a reservoir of water, the ${\mathrm{FeSiO}}_4{\mathrm{H}}_2$ can enter the lower mantle and release water through the disproportionation of ferrous iron, which occurs during the accretion process. Our findings provide a different perspective on the behavior of the Earth's interior and expose more possibilities for the evolution models of terrestrial planets in our solar system and beyond.

Close

PrevNext

View figure in article

• Crystal structure
• Earth's interior
• Pressure effects
• Structural phase transition
• First-principles calculations