Structure and stability of Fe4C bulk and surfaces: A density functional theory study

Density functional theory calculations have been performed on the structure and stability of Fe4C bulk and the corresponding low-index surfaces. It is found that the structure with octahedral interstitial carbon (Fe4C/oct) is more stable than that with tetrahedral interstitial carbon (Fe4C/tet). For Fe4C/oct, the most stable surface termination is the (1 0 0) surface with mixed carbon and iron (TFe/C). For Fe4C/tet, the most stable surface termination is the dramatically reconstructed (1 1 0) surface with the newly formed TFe/C surface layer.