Reverse chemistry of iron in the deep Earth

TL;DR

This paper reveals that under high pressure, iron changes from an electron donor to an acceptor, significantly affecting the chemistry and structure of deep Earth compounds, with implications for Earth's composition.

Contribution

It introduces a systematic first-principles study showing the pressure-induced reversal in iron's chemical behavior in Earth's deep interior.

Findings

Iron reverses from reductant to oxidant under high pressure.

Pressure alters stoichiometries and bond types in iron compounds.

Reversal impacts Earth's mantle and core chemistry.

Abstract

In this work, we demonstrate a remarkable change of chemical trend of Iron under high pressure that is of great importance for understanding the distribution of elements in the Earth's mantle and core. Using first principles crystal structure search method, we conduct a systematic study of the propensity of p block elements to chemically bind with iron under high pressures ranging from ambient conditions to that of Earth's core. We show that under increasing pressure, iron tends to reverse its chemical nature, changing from an electron donor (reductant) to an electron acceptor, and oxidizes p-block elements in many compounds. Such reverse chemistry has a significant impact on the stoichiometries, bond types and strengths, structures and properties of iron compounds under deep planetary conditions.