## Atomistic modelling of the interaction of dislocations with point defects in iron and steel

Extended defects in iron and the influence of carbon on them on an atomistic scale are of special interest for the understanding of plasticity in steel. Despite their accuracy, due to efficiency reasons ab-initio methods are not suitable to calculate defects like dislocations.

The Bond-Order Potential (BOP) for magnetic transition metals on the other hand is an interatomic potential obtained from a systematic coarse-graining of the electronic structure from density functional theory (DFT) over tight binding (TB) to the given BOP, that is able to calculate large scale systems of up to a million atoms. Since it preserves fundamental electronic properties this potential provides a tool to gain physical insights in chemical and magnetic effects while scaling linearly with system size like the commonly used interatomic potentials, e.g. the embedded atom methods (EAM). Thus the descriptions of chemical bonding in TB models of Fe and Fe-C developed at ICAMS serve as the foundation for BOP parameterizations and calculations of large systems and possible characterizations of extended defects.