Journal
NEW JOURNAL OF PHYSICS
Volume 23, Issue 6, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/1367-2630/ac0287
Keywords
FeMgO; crystal structure prediction; high pressure; first-principles calculation
Categories
Funding
- National Science Foundation [EAR-1918134, EAR-1918126]
- Extreme Science and Engineering Discovery Environment (XSEDE) - National Science Foundation [ACI-1548562]
- Department of Energy Theoretical Chemistry Program [DOE-DESC0019759]
- National Natural Science Foundation of China [11774324, 12074362, 11874307]
- Supercomputing Center of USTC
- Guangdong Natural Science Foundation of China [2017B030306003, 2019B1515120078]
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The study used the adaptive genetic algorithm to investigate Fe Mg-x(y) O-z phases under high pressures, identifying three dynamically stable phases; a ternary convex hull for Fe-Mg-O was constructed, clarifying the composition- and pressure-dependence of structural motifs; analysis suggests that O, Mg, or both could stabilize a BCC iron alloy at inner core pressures.
Fe, Mg, and O are among the most abundant elements in terrestrial planets. While the behavior of the Fe-O, Mg-O, and Fe-Mg binary systems under pressure have been investigated, there are still very few studies of the Fe-Mg-O ternary system at relevant Earth's core and super-Earth's mantle pressures. Here, we use the adaptive genetic algorithm (AGA) to study ternary Fe Mg-x(y) O-z phases in a wide range of stoichiometries at 200 GPa and 350 GPa. We discovered three dynamically stable phases with stoichiometries FeMg2O4, Fe2MgO4, and FeMg3O4 with lower enthalpy than any known combination of Fe-Mg-O high-pressure compounds at 350 GPa. With the discovery of these phases, we construct the Fe-Mg-O ternary convex hull. We further clarify the composition- and pressure-dependence of structural motifs with the analysis of the AGA-found stable and metastable structures. Analysis of binary and ternary stable phases suggest that O, Mg, or both could stabilize a BCC iron alloy at inner core pressures.
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