A cotunnite-type new high-pressure phase of Fe2S

Kenta Oka, Shigehiko Tateno, Yasuhiro Kuwayama, Kei Hirose, Yoichi Nakajima, Koihiro Umemoto, Noriyoshi Tsujino, Saori I. Kawaguchi

Research output: Contribution to journalArticlepeer-review


We examined pressure-induced phase transitions in Fe2S based on high-pressure and high-temperature X-ray diffraction measurements in a laser-heated diamond-anvil cell. Fe2S is not stable at ambient pressure but is known to form above 21 GPa with the Fe2P-type (C22) structure. Our experiments demonstrate a novel phase transition in Fe2S from the C22 to C23 phase with the Co2P-type cotunnite structure above ~30 GPa. The experiments also reveal a transformation from the C23 to C37 (Co2Si-type) phase above ~130 GPa. While the C23 and C37 structures exhibit the same crystallographic symmetry (orthorhombic Pnma), the coordination number of sulfur increases from nine in C23 to ten in C37. Such a sequence of pressure-induced phase transitions in Fe2S, C22 → C23 → C37, are similar to those of Fe2P, while they are not known in oxides and halogens that often adopt the C23 cotunnite-type structure. The newly found cotunnite-type Fe2S phase could be present in solid iron cores of planets, including Mars.

Original languageEnglish
Pages (from-to)1249-1253
Number of pages5
JournalAmerican Mineralogist
Issue number7
Publication statusPublished - Jul 1 2022
Externally publishedYes


  • Iron sulfide
  • Mars
  • Physics and Chemistry of Earth's Deep Mantle and Core
  • core
  • cotunnite-type structure
  • high pressure
  • high temperature
  • phase transition

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology


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