Stability, structure and electronic properties of γ-Fe23C6 from first-principles theory / C.M. Fang in Acta materialia, Vol. 58 N° 8 (Mai 2010)  

Public ISBD [article]  inActa materialia > Vol. 58 N° 8 (Mai 2010) . - pp. 2968–2977 Titre : Stability, structure and electronic properties of γ-Fe23C6 from first-principles theory Type de document : texte imprimé Auteurs : C.M. Fang, Auteur ; M.A. van Huis, Auteur ; M.H.F. Sluiter, Auteur Année de publication : 2011 Article en page(s) : pp. 2968–2977 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Iron carbides First-principles’ calculations Crystal structure Stability and formation Résumé : First-principles’ calculations of GGA and GGA + U type have been performed for γ-Fe23C6, a complex iron carbide with 116 atom in the unit cell. GGA results were found to be in better agreement with experimental data than GGA + U results. Various occupancies for Wyckoff positions and corresponding magnetic orderings have been explored. Our calculations reveal that the crystal structure is composed of a framework of strongly linked Fe atoms, and additional stabilizing Fe and C atoms positioned in cavities. The local electronic and magnetic properties vary strongly among the non-equivalent Fe sites in γ-Fe23C6. The lattice parameters of γ-Fe23C6 match those of austenite well. Surprisingly, pure γ-Fe23C6 is found to be more stable than commonly occurring θ-Fe3C cementite. Moreover, the calculations show low vacancy energy (about 0.37 eV) for Fe at 4a sites in γ-Fe23C6. Conditions of formation and factors hampering the formation of γ-Fe23C6 in steel manufacturing processes are discussed. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S135964541000039X [article] Stability, structure and electronic properties of γ-Fe23C6 from first-principles theory [texte imprimé] / C.M. Fang, Auteur ; M.A. van Huis, Auteur ; M.H.F. Sluiter, Auteur . - 2011 . - pp. 2968–2977. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 8 (Mai 2010) . - pp. 2968–2977 Mots-clés : Iron carbides First-principles’ calculations Crystal structure Stability and formation Résumé : First-principles’ calculations of GGA and GGA + U type have been performed for γ-Fe23C6, a complex iron carbide with 116 atom in the unit cell. GGA results were found to be in better agreement with experimental data than GGA + U results. Various occupancies for Wyckoff positions and corresponding magnetic orderings have been explored. Our calculations reveal that the crystal structure is composed of a framework of strongly linked Fe atoms, and additional stabilizing Fe and C atoms positioned in cavities. The local electronic and magnetic properties vary strongly among the non-equivalent Fe sites in γ-Fe23C6. The lattice parameters of γ-Fe23C6 match those of austenite well. Surprisingly, pure γ-Fe23C6 is found to be more stable than commonly occurring θ-Fe3C cementite. Moreover, the calculations show low vacancy energy (about 0.37 eV) for Fe at 4a sites in γ-Fe23C6. Conditions of formation and factors hampering the formation of γ-Fe23C6 in steel manufacturing processes are discussed. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S135964541000039X

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