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Fe — C and Fe — H systems at pressures of the Earth’s inner core

 a,  b,  c
a Scientific Research Computer Center, Lomonosov Moscow State University, Leninskiye Gory 1, building 4, Moscow, 119991, Russian Federation
b Department of Geosciences and Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York, USA
c Institut für Geochemie und Petrologie, Department of Earth Sciences, ETH Zürich, Clausiusstrasse 25, 8092, Zürich, Switzerland

The solid inner core of Earth is predominantly composed of iron alloyed with several percent Ni and some lighter elements, Si, S, O, H, and C being the prime candidates. To establish the chemical composition of the inner core, it is necessary to find the range of compositions that can explain its observed characteristics. Recently, there have been a growing number of papers investigating C and H as possible light elements in the core, but the results were contradictory. Here, using ab initio simulations, we study the Fe—C and Fe—H systems at inner core pressures (330–364 GPa). Based on the evolutionary structure prediction algorithm USPEX, we have determined the lowest-enthalpy structures of all possible carbides (FeC, Fe2C, Fe3C, Fe4C, FeC2, FeC3, FeC4, Fe73) and hydrides (Fe4H, Fe3H, Fe2H, FeH, FeH2, FeH3, FeH4) and have found that Fe2C (space group Pnma) is the most stable iron carbide at pressures of the inner core, while FeH, FeH3, and FeH4 are the most stable iron hydrides at these conditions. For Fe3C, the cementite structure (space group Pnma) and the Cmcm structure recently found by random sampling are less stable than the I-4 and C2 /m structures predicted here. We have found that FeH3 and FeH4 adopt chemically interesting thermodynamically stable crystal structures, containing trivalent iron in both compounds. We find that the density of the inner core can be matched with a reasonable concentration of carbon, 11–15 mol.% (2.6–3.7 wt.%) at relevant pressures and temperatures, yielding the upper bound to the C content in the inner core. This concentration matches that in CI carbonaceous chondrites and corresponds to the average atomic mass in the range 49.3–51.0, in close agreement with inferences from Birch’s law for the inner core. Similarly made estimates for the maximum hydrogen content are unrealistically high: 17–22 mol.% (0.4–0.5 wt.%), which corresponds to the average atomic mass of the core in the range 43.8–46.5. We conclude that carbon is a better candidate light alloying element than hydrogen.

Fulltext is available at IOP
PACS: 61.50.Ah, 61.50.Ks, 61.50.Nw, 61.66.Fn, 64.30.−t, 91.60.Fe (all)
DOI: 10.3367/UFNe.0182.201205c.0521
URL: https://ufn.ru/en/articles/2012/5/c/
Citation: Bazhanova Z G, Oganov A R, Gianola O "Fe — C and Fe — H systems at pressures of the Earth's inner core" Phys. Usp. 55 489–497 (2012)
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Received: 13th, December 2011, revised: 22nd, February 2012, 17th, February 2012

Оригинал: Бажанова З Г, Оганов А Р, Джанола О «Системы Fe — C и Fe — H при давлениях внутреннего ядра Земли» УФН 182 521–530 (2012); DOI: 10.3367/UFNr.0182.201205c.0521

References (72) ↓ Cited by (48) Similar articles (5)

  1. Birch F J. Geophys. Res. 69 4377 (1964)
  2. Stevenson D J Science 214 611 (1981)
  3. Jeanloz R Annu. Rev. Earth Planet. Sci. 18 357 (1990)
  4. Birch F J. Geophys. Res. 57 227 (1952)
  5. Poirier J-P Introduction To The Physics Of The Earth’s Interior 2nd ed. (Cambridge: Cambridge Univ. Press, 2000)
  6. Buchwald V F Handbook Of Iron Meteorites, Their History, Distribution, Composition, And Structure Vol. 1 (Berkeley, Calif.: Univ. of California Press, 1975)
  7. Jephcoat A, Olson P Nature 325 332 (1987)
  8. Poirier J-P Phys. Earth Planet. Int. 85 319 (1994)
  9. Wood B J Earth Planet. Sci. Lett. 117 593 (1993)
  10. Tingle T N Chem. Geol. 147 3 (1998)
  11. Hirayama Y, Fujii T, Kurita K Geophys. Res. Lett. 20 2095 (1993)
  12. McDonough W F Treatise On Geochemistry Vol. 2 (Ed. R W Carlson) (Amsterdam: Elsevier, 2003) p. 547
  13. Hillgren V J, Gessmann C K, Li J Origin Of The Earth And Moon (Eds R M Canup, K Righter) (Tucson: Univ. of Arizona Press, 2000) p. 245
  14. Anisichkin V F Combust. Explosion Shock Waves 36 516 (2000)
  15. Huang L et al. Geophys. Res. Lett. 32 L21314 (2005)
  16. Oganov A R et al. Earth Planet. Sci. Lett. 273 38 (2008)
  17. Tateno S et al. Science 330 359 (2010)
  18. Li J et al. Phys. Chem. Minerals 29 166 (2002)
  19. Scott H, Williams Q, Knittle E Geophys. Res. Lett. 28 1875 (2001)
  20. Vočadlo L et al. Earth Planet. Sci. Lett. 203 567 (2002)
  21. Lin J-F et al. Phys. Rev. B 70 212405 (2004)
  22. Sata N et al. J. Geophys. Res. 115 B09204 (2010)
  23. Nakajima Y et al. Phys. Earth Planet. Inter. 174 202 (2009)
  24. Fiquet G et al. Phys. Earth Planet. Inter. 172 125 (2009)
  25. Gao L et al. Geophys. Res. Lett. 35 L17306 (2008)
  26. Rouquette J et al. Appl. Phys. Lett. 92 121912 (2008)
  27. Lord O T et al. Earth Planet. Sci. Lett. 284 157 (2009)
  28. Nakajima Y et al. Am. Mineral. 96 1158 (2011)
  29. Mookherjee M et al. J. Geophys. Res. 116 B04201 (2011)
  30. Weerasinghe G L, Needs R J, Pickard C J Phys. Rev. B 84 174110 (2011)
  31. Freeman C M et al. J. Mater. Chem. 3 531 (1993)
  32. Fukai Y et al. Jpn. J. Appl. Phys. 318 (1982)
  33. Badding J V, Mao H K, Hemley R J High-Pressure Research (Geophysical Monograph Ser.) Vol. 67 (Eds Y Syono, M H Manghnani) (Washington, DC: Terra Sci. Publ. Co./American Geophysical Union, 1992) p. 363
  34. Badding J V, Hemley R J, Mao H K Science 253 421 (1991)
  35. Yamakata M et al. Proc. Jpn. Acad. B 68 172 (1992)
  36. Fukai Y, Yamakata M, Yagi T Z. Phys. Chem. N.F. 179 119 (1993)
  37. Hirao N et al. Geophys. Res. Lett. 31 L06616 (2004)
  38. Isaev E I et al. Proc. Natl. Acad. Sci. USA 104 9168 (2007)
  39. Skorodumova N V, Ahuja R, Johansson B Geophys. Res. Lett. 31 L08601 (2004)
  40. Fukai Y Nature 308 174 (1984)
  41. Mao W L et al. Geophys. Res. Lett. 31 L15618 (2004)
  42. Elsässer C et al. J. Phys. Condens. Matter 10 5113 (1998)
  43. Stevenson D J Nature 268 130 (1977)
  44. Yagi T, Hishinuma T Geophys. Res. Lett. 22 1933 (1995)
  45. Okuchi T Science 278 1781 (1997)
  46. Narygina O et al. Earth Planet. Sci. Lett. 307 409 (2011)
  47. Oganov A R, Glass C W J. Chem. Phys. 124 244704 (2006)
  48. Glass C W, Oganov A R, Hansen N Comput. Phys. Commun. 175 713 (2006)
  49. Lyakhov A O, Oganov A R, Valle M Comput. Phys. Commun. 181 1623 (2010)
  50. Oganov A R, Lyakhov A O, Valle M Acct. Chem. Res. 44 227 (2011)
  51. Hohenberg P, Kohn W Phys. Rev. 136 B864 (1964)
  52. Kohn W, Sham L J Phys. Rev. 140 A1133 (1965)
  53. Perdew J P, Burke K, Ernzerhof M Phys. Rev. Lett. 77 3865 (1996)
  54. Hemley R J, Mao H K Int. Geol. Rev. 43 1 (2001)
  55. Ma Y et al. Phys. Earth Planet. Inter. 143-144 455 (2004)
  56. Pickard C J, Needs R J Nature Phys. 3 473 (2007)
  57. Blöchl P E Phys. Rev. B 50 17953 (1994)
  58. Kresse G, Joubert D Phys. Rev. B 59 1758 (1999)
  59. Kresse G, Furthmüller J Phys. Rev. B 54 11169 (1996)
  60. Methfessel M, Paxton A T Phys. Rev. B 40 3616 (1989)
  61. Brown I D Acta Cryst. B 48 553 (1992)
  62. Zurek E et al. Proc. Natl. Acad. Sci. 106 17640 (2009)
  63. Gao G et al. Phys. Rev. Lett. 101 107002 (2008)
  64. Gao G et al. Proc. Natl. Acad. Sci. 107 1317 (2010)
  65. Alfè D et al. Philos. Trans. R. Soc. Lond. A 360 1227 (2002)
  66. Dewaele A et al. Phys. Rev. Lett. 97 215504 (2006)
  67. Occelli F, Loubeyre P, LeToullec R Nature Mater. 2 151 (2003)
  68. Dziewonski A M, Anderson D L Phys. Earth Planet. Inter. 25 297 (1981)
  69. Oganov A R, Brodholt J P, Price G D Earth Planet. Sci. Lett. 184 555 (2001)
  70. Alfè D, Kresse G, Gillan M J Phys. Rev. B 61 132 (2000)
  71. Alfè D, Gillan M J, Price G D Earth Planet. Sci. Lett. 195 91 (2002)
  72. Zhang F, Oganov A R Geophys. Res. Lett. 37 L02305 (2010)

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