Solid phases of FeSi to 47 GPa and 2800 K; new data

FeSi remains crystalline up to at least 2350 (+ or -200) K at 23 GPa and 2770 (+ or -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 (+ or -100) K to 2700 (+ or -150) K between 20 and 50 GPa. The transition between epsilon (B20) and B2 (CsCl-structured) crystalline phases occurs at 30 (+ or -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.