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Elasticity and anisotropy of iron‐nickel phosphides at high pressures
Author(s) -
Wu Xiang,
Mookherjee Mainak,
Gu Tingting,
Qin Shan
Publication year - 2011
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2011gl049158
Subject(s) - nickel , materials science , anisotropy , ferromagnetism , meteorite , thermodynamics , condensed matter physics , crystallography , analytical chemistry (journal) , metallurgy , chemistry , physics , astrobiology , quantum mechanics , chromatography
Geochemical estimates indicate that around 90% of the planet's inventory of phosphorus is likely to be sequestered in the Earth's core. Iron phosphides such as scheirbisites (Fe 3 P) are commonly found in iron meteorites. Recently, melliniite (Fe,Ni) 4 P with 12.2 wt% phosphorus has been reported in iron‐meteorites. Using static electronic structure calculations, we predict that Fe 4 P is unlikely to dissociate into Fe 3 P and hcp Fe at inner core conditions. Among the different structural varieties of Fe 4 P, we find the cubic polymorph with P 2 1 3 space group symmetry to be stable over a wide range of geophysically relevant pressures. We have determined the equation of state and the full elastic constant tensor of the stable (Fe,Ni) 4 P phase at pressures up to 400 GPa. Upon compression, Fe 4 P undergoes a ferromagnetic ( fm ) to nonmagnetic ( nm ) transition at 80 GPa. In nonmagnetic (Fe,Ni) 4 P, nickel incorporation results in reduction of the P‐ and S‐wave velocities. However, incorporation of nickel enhances the P‐ and S‐wave anisotropy.