Premium
Stability and compressibility of a new iron‐nitride β ‐Fe 7 N 3 to core pressures
Author(s) -
Minobe Sayuri,
Nakajima Yoichi,
Hirose Kei,
Ohishi Yasuo
Publication year - 2015
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 - 10.1002/2015gl064496
Subject(s) - inner core , diamond anvil cell , materials science , diffraction , compressibility , phase (matter) , nitride , diamond , outer core , crystallography , iron nitride , core (optical fiber) , thermodynamics , mineralogy , chemistry , metallurgy , composite material , physics , optics , organic chemistry , layer (electronics)
Abstract We have examined the phase relations in the iron‐rich portion of the Fe‐N binary system up to 150 GPa and 2720 K in a laser‐heated diamond anvil cell. Synchrotron X‐ray diffraction measurements revealed the formation of a new phase ( β ‐Fe 7 N 3 ) above 41 GPa and ~1000 K. The β phase is structurally identical or very close to Fe 7 C 3 and the most iron‐rich Fe‐N intermediate compound at its stability field. We also measured the volume of β ‐Fe 7 N 3 to 132 GPa and found its elastic property very similar to that of Fe 7 C 3 . Recently, it has been proposed that the density and sound velocities, in particular, shear wave velocity, in the Earth's inner core are reconciled with Fe 7 C 3 , but such properties could be explained by β ‐Fe 7 N 3 equally well. It is therefore possible that the inner core consists of Fe 7 (C,N) 3 , which is found as diamond inclusions and likely stable under inner core conditions.