New high-pressure phases of Fe7N3 and Fe7C3 stable at Earth's core conditions: evidences for carbon-nitrogen isomorphism in Fe-compounds

Nursultan Sagatov, Pavel N. Gavryushkin, Talgat M. Inerbaev, Konstantin D. Litasov

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

We carried out ab initio calculations on the crystal structure prediction and determination of P-T diagrams within the quasi-harmonic approximation for Fe7N3 and Fe7C3. Two new isostructural phases Fe7N3-C2/m and Fe7C3-C2/m which are dynamically and thermodynamically stable under the Earth's core conditions were predicted. The Fe7C3-C2/m phase stabilizes preferentially to the known h-Fe7C3 at 253-344 GPa in the temperature range of 0-5000 K, and the Fe7N3-C2/m stabilizes preferentially relative to the β-Fe7N3-at ∼305 GPa over the entire temperature range. This indicate that carbon and nitrogen can mutually coexist and replace each other in the Earth's and other planetary cores similarly to low pressure phases of the same compounds.

Original languageEnglish
Pages (from-to)3577-3581
Number of pages5
JournalRSC Advances
Volume9
Issue number7
DOIs
Publication statusPublished - 29 Jan 2019

Keywords

  • CRYSTAL-STRUCTURE PREDICTION
  • TOTAL-ENERGY CALCULATIONS
  • EQUATION-OF-STATE
  • IRON NITRIDES
  • CARBIDE
  • GPA

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