Issues

 / 

2017

 / 

October

  

Methodological notes


High-pressure behavior of the Fe—S system and composition of the Earth's inner core

 a,  b,  c, b, a
a Lomonosov Moscow State University, Vorobevy Gory, Moscow, 119991, Russian Federation
b Moscow Institute of Physics and Technology (National Research University), Institutskii per. 9, Dolgoprudny, Moscow Region, 141701, Russian Federation
c Skolkovo Institute of Science and Technology, Bolshoy Boulevard 30, bld. 1, Moscow, 121205, Russian Federation

Using evolutionary crystal structure prediction algorithm USPEX, we identify the compositions and crystal structures of stable compounds in the Fe—S system at pressures in the range 100—400 GPa. We find that at pressures of the Earth's solid inner core (330—364 GPa) two compounds are stable — Fe2S and FeS. In equilibrium with iron, only Fe2S can exist in the inner core. Using the equation of state of Fe2S, we find that in order to reproduce the density of the inner core by adding sulfur alone, 10.6—13.7 mol.% (6.4—8.4 wt.%) sulfur is needed. Analogous calculation for silicon (where the only stable compound at inner core pressures is FeSi) reproduces the density of the inner core with 9.0—11.8 mol.% (4.8—6.3 wt.%) silicon. In both cases, a virtually identical mean atomic mass $\bar M$ in the range 52.6—53.3 results for in the inner core, which is much higher than $\bar M=49.3$ determined for the inner core from Birch's law. In the case of oxygen (noting the equilibrium coexistence of suboxide Fe2O with iron under nuclear conditions), the inner core density can be explained by the hydrogen content of 13.2—17. 2 mol.% (4.2—5.6 mass%), which corresponds to $\bar M$ between 49.0 and 50.6. Combining our results and previous works, we arrive at four preferred compositional models of the inner core (in atomic %): (i) 86% (Fe+Ni)+14% C; (ii) 84% (Fe+Ni)+16% O; (iii) 84% (Fe+Ni)+7% S+9% H; (iv) 85% (Fe+Ni)+6% Si+9% H.

Fulltext pdf (632 KB)
Fulltext is also available at DOI: 10.3367/UFNe.2017.03.038079
Keywords: crystal structure prediction, ab initio calculations, evolutionary algorithms, mineral physics
PACS: 61.50.Ah, 61.50.Ks, 61.50.Nw, 61.66.Fn, 64.30.−t, 91.60.Fe (all)
DOI: 10.3367/UFNe.2017.03.038079
URL: https://ufn.ru/en/articles/2017/10/d/
000419110600004
2-s2.0-85040925889
Citation: Bazhanova Z G, Roizen V V, Oganov A R "High-pressure behavior of the Fe—S system and composition of the Earth's inner core" Phys. Usp. 60 1025–1032 (2017)
BibTexBibNote ® (generic)BibNote ® (RIS)MedlineRefWorks

Received: 6th, February 2017, revised: 21st, February 2017, 2nd, March 2017

Оригинал: Бажанова З Г, Ройзен В В, Оганов А Р «Поведение системы Fe—S при высоких давлениях и состав ядра Земли» УФН 187 1105–1113 (2017); DOI: 10.3367/UFNr.2017.03.038079

References (72) Cited by (21) Similar articles (19) ↓

  1. Yu.Kh. Vekilov, O.M. Krasil’nikov, A.V. Lugovskoy “Elastic properties of solids at high pressure58 1106–1114 (2015)
  2. V.N. Zharkov “On estimating the molecular viscosity of the Earth’s outer core: comment on the paper by D E Smylie et al.52 93–95 (2009)
  3. D.E. Smylie, V.V. Brazhkin, A. Palmer “Direct observations of the viscosity of Earth’s outer core and extrapolation of measurements of the viscosity of liquid iron52 79–92 (2009)
  4. Yu.Kh. Vekilov, O.M. Krasil’nikov et alElastic phase transitions in metals at high pressures57 897–902 (2014)
  5. Yu.Kh. Vekilov, O.M. Krasil’nikov “Structural transformations in metals at high compression ratios52 831–834 (2009)
  6. S.E. Kuratov, D.S. Shidlovski et alTwo scales of quantum effects in a mesoscopic system of degenerate electrons64 836–851 (2021)
  7. V.V. Brazhkin, R.N. Voloshin et alPhase equilibria in partially open systems under pressure: the decomposition of stoichiometric GeO2 oxide46 1283–1289 (2003)
  8. B.M. Smirnov “Clusters with close packing35 (1) 37–48 (1992)
  9. V.B. Priezzhev “The dimer problem and the Kirchhoff theorem28 1125–1135 (1985)
  10. I.D. Novikov “Antigravitation in the Universe61 692–696 (2018)
  11. G.S. Paiva, J.V. Ferreira et alEnergy density calculations for ball-lightning-like luminous silicon balls53 209–213 (2010)
  12. D.E. Smylie, V.V. Brazhkin, A. Palmer “Reply to comment by V N Zharkov “On estimating the molecular viscosity of the Earth’s outer core”52 96–96 (2009)
  13. V.I. Alshits, V.N. Lyubimov “Generalization of the Leontovich approximation for electromagnetic fields on a dielectric — metal interface52 815–820 (2009)
  14. A.I. Frank “On the properties of the "potential" neutron dispersion law in a refractive medium61 900–901 (2018)
  15. V.V. Brazhkin “Why does statistical mechanics 'work' in condensed matter?64 1049–1057 (2021)
  16. A.N. Herega, N.G. Drik, A.P. Ugol’nikov “Hybrid ramified Sierpinski carpet: percolation transition, critical exponents, and force field55 519–521 (2012)
  17. E.G. Maksimov, O.V. Dolgov “A note on the possible mechanisms of high-temperature superconductivity50 933–937 (2007)
  18. A.A. Logunov “The theory of the classical gravitational field38 179–193 (1995)
  19. G.T. Zatsepin, Yu.A. Nechin, G.B. Khristiansen “Use of the magnetic induction of iron in cosmic-ray and high-energy physics30 1007–1008 (1987)

The list is formed automatically.

© 1918–2024 Uspekhi Fizicheskikh Nauk
Email: ufn@ufn.ru Editorial office contacts About the journal Terms and conditions