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Constraints on the crystalline structure of the inner core: Mechanical instability of BCC iron at high pressure
Author(s) -
Stixrude Lars,
Cohen R. E.
Publication year - 1995
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 - 10.1029/94gl02742
Subject(s) - inner core , tetragonal crystal system , instability , materials science , core (optical fiber) , phase (matter) , outer core , high pressure , equation of state , condensed matter physics , energetics , electronic structure , phase transition , crystal structure , thermodynamics , crystallography , physics , chemistry , mechanics , composite material , quantum mechanics
We examine the energetics of close‐packed phases of iron (bcc, fcc, hcp) throughout the pressure regime of the earth with elaborate first principles electronic structure calculations. The calculations reproduce the relevant experimental observations including the equation of state to over 300 GPa and the pressure of the bcc to hcp phase transition. The bcc structure is found to be energetically unfavorable and mechanically unstable with respect to a tetragonal strain at high pressure (P>150 GPa). This phase is thus highly unlikely to exist in the earth's inner core as has frequently been proposed.