Unconventional iron-magnesium compounds at terapascal pressures

TL;DR

This study explores the formation and structure of unconventional iron-magnesium compounds under terapascal pressures, revealing new phases and packing motifs relevant to exoplanetary science.

Contribution

It extends high-pressure phase predictions of Fe-Mg compounds to 3 TPa using an adaptive genetic algorithm, identifying new phases and structural motifs.

Findings

Several Fe-Mg phases identified up to 3 TPa

Most compounds favor BCC packing at terapascal pressures

Provides a comprehensive structure database for high-pressure Fe-Mg research

Abstract

Being a lithophile element at ambient pressure, magnesium is long believed to be immiscible with iron. A recent study by Gao et al. [1] showed that pressure turns magnesium into a siderophile element and can produce unconventional Fe-Mg compounds. Here, we extend the investigation to exoplanetary pressure conditions using an adaptive genetic algorithm-based variable-composition structural prediction approach. We identify several Fe-Mg phases up to 3 TPa. Our cluster alignment analysis reveals that most of the predicted Fe-Mg compounds prefer a BCC packing motif at terapascal pressures. This study provides a more comprehensive structure database to support future investigations of the high-pressure structural behavior of Fe-Mg and ternary, quaternary, etc. compounds involving these elements.