Compression of Fe–Si–H alloys to core pressures

Abstract

Abstract We examined the compression behavior of hexagonal‐close‐packed (hcp) (Fe 0.88 Si 0.12 ) 1 H 0.61 and (Fe 0.88 Si 0.12 ) 1 H 0.79 (in atomic ratio) alloys up to 138 GPa in a diamond anvil cell (DAC). While contradicting experimental results were previously reported on the compression curve of double‐hcp (dhcp) FeH x ( x ≈ 1), our data show that the compressibility of hcp Fe 0.88 Si 0.12 H x alloys is very similar to those of hcp Fe and Fe 0.88 Si 0.12 , indicating that the incorporation of hydrogen into iron does not change its compression behavior remarkably. The present experiments suggest that the inner core may contain up to 0.47 wt % hydrogen (FeH 0.26 ) if temperature is 5000 K. The calculated density profile of Fe 0.88 Si 0.12 H 0.17 alloy containing 0.32 wt % hydrogen in addition to geochemically required 6.5 wt % silicon matches the seismological observations of the outer core, supporting that hydrogen is an important core light element.