FeSi remains crystalline up to at least 2350 (±200) K at 23 GPa and 2770 (±200) K at 47 GPa in a laser-heated diamond-anvil cell, showing that addition of silicon does not cause a large amount of melting point depression; the melting temperature of pure iron ranges from 2300 (±100) K to 2700 (±150) K between 20 and 50 GPa. The transition between ɛ (B20) and B2 (CsCl-structured) crystalline phases occurs at 30 (±2) GPa at all temperatures from 1200 to 2400 K. The resulting 5% density increase may cause an increase in the miscibility of silicon in iron at P > 30 GPa, with potential implications for the cores of small rocky planets such as Mars and Mercury.

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