Abstract
The Earth’s inner core comprises iron-nickel alloys with light elements. However, there is no clarity on the phase properties of these alloys. Here we show phase relations and equations of state of iron–nickel and iron–nickel–silicon alloys up to 186 gigapascals and 3090 kelvin. An ordered derivative of the body-centred cubic structure (B2) phase was observed in these alloys. Results show that nickel and silicon influence the stability field associated with the two-phase mixture of B2 and hexagonal close-packed phases under core conditions. The two-phase mixture can give the inner core density of the preliminary reference Earth model. The compressional wave velocity of the two-phase mixture under inner core conditions is consistent with that of the preliminary reference Earth model. Therefore, a mixture of B2 and hexagonal close-packed phases may exist in the inner core and accounts for the seismological properties of the inner core such as density and velocity deficits.
Highlights
The Earth’s inner core comprises iron-nickel alloys with light elements
Silicon (Si) is one of the most plausible light elements to be considered as a part of the inner core composition because it exists in the form of iron alloys in iron meteorites and is depleted in the Earth’s mantle when compared to its abundance in chondrites[5]
Results show that the two-phase mixture elucidates the inner core density of the preliminary reference Earth model (PREM)
Summary
The Earth’s inner core comprises iron-nickel alloys with light elements. there is no clarity on the phase properties of these alloys. Results show that nickel and silicon influence the stability field associated with the two-phase mixture of B2 and hexagonal close-packed phases under core conditions. The compressional wave velocity of the two-phase mixture under inner core conditions is consistent with that of the preliminary reference Earth model. A mixture of B2 and hexagonal close-packed phases may exist in the inner core and accounts for the seismological properties of the inner core such as density and velocity deficits. Results show that the two-phase mixture elucidates the inner core density of the preliminary reference Earth model (PREM). It is concluded that the inner core may be composed of a mixture of B2 and hcp phases, which explains the seismological properties of the inner core in terms of its density and velocity deficits
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