ω structure in steel: A first-principles study

• Stability of the ω structure in steel and effects of interstitial C atoms are investigated based on first-principles.
• The interstitial C atoms increase the energy of the ω structure compared with the ferromagnetic (FM) BCC.
• The ω structure incorporating C atoms is also mechanically unstable unless the C concentration is 25 at.%.
• The ω structure in steel may be formed under special atomic constraints at twin boundaries or other interfaces.

Recent experimental works reported observation of the ω structure in steel. Here, stability of the ω structure in steel is investigated based on first-principles with special interests in effects of interstitial C atoms. The interstitial C atoms increase the energy of the ω structure compared with the ferromagnetic (FM) BCC. The ω structure incorporating C atoms is also dynamically unstable unless the C concentration is 25 at.%. It is concluded that the ω structure is mostly unstable in steel, and the ω structure in steel may be formed under special atomic constraints at twin boundaries or other interfaces.

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