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Abstract

Parameterized methods to extend electronic structure calculations to large systems have recently garnered additional attention due to the limits of traditional DFT. The ability to model low carbon content in steel requires the accurate calculation of millions of atoms. However, interatomic potentials have been shown to be inconsistent with DFT in different environments and cannot give an accurate portrayal of chemical bonding or magnetism. Thus, a coherent transferable tight-binding (TB) parameterization was developed for Fe-C by extracting bonding interactions from DFT and finding a suitable interatomic repulsion. This model gives an accurate description of the energy hierarchy of relevant Fe-C structures, elastic properties, and defect energies. We apply this model to determine mechanisms of carbon segregation to grain boundaries and carbon diffusion in iron, including the interaction of multiple defects under tension and pressure. Furthermore, this intuitive energy functional forms the basis for bond order potentials, thereby extending system sizes to millions of atoms.