Parameterized electronic description of carbon cohesion in iron grain boundaries

• Published in: Journal of physics. Condensed matter 2014-04, Vol.26 (14), p.145502-145502
• Main Authors: Hatcher, Nicholas, Madsen, Georg K H, Drautz, Ralf
• Format: Article
• Language: English
• Subjects: Carbon; Carbon - chemistry; Computer Simulation; Condensed matter; Electromagnetic Fields; Electronics; Grain boundaries; grain boundary; Iron; Iron - chemistry; Mathematical models; Models, Chemical; Models, Molecular; Nanostructures; Nuclear power generation; Particle Size; segregation; Segregations; Surface Properties; tight-binding
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/26/14/145502

We employ a recently developed iron-carbon orthogonal tight-binding model in calculations of carbon in iron grain boundaries. We use the model to evaluate the properties of carbon near and on the Σ5 (3 1 0)[0 0 1] symmetric tilt grain boundary (GB) in iron, and calculations show that a carbon atom lowers the GB energy by 0.29 eV/atom in accordance with DFT. Carbon segregation to the GB is analyzed, and we find an energy barrier of 0.92 eV for carbon to segregate to the carbon-free interface while segregation to a fully filled interface is disfavored. Local volume (via Voronoi tessellation), magnetic, and electronic effects are correlated with atomic energy changes, and we isolate two different mechanisms governing carbon's behavior in iron: a volumetric strain which increases the energy of carbon in interstitial α iron and a non-strained local bonding which stabilizes carbon at the GB.