Core Energies in Isolated Edge and Mixed Dislocations in BCC Fe from First-principles Energy Density Method

Abstract

We use first-principles spin-polarized energy density method (EDM) to calculate the atomic energies in isolated $a_0[100](010)$ edge, $a_0[100](011)$ edge, $\frac{a_0}{2}[\bar1\bar11](1\bar10)$ edge and $\frac{a_0}{2}[111](1\bar10)$ $71^\circ$ mixed dislocations in body-centered cubic (BCC) Fe. The distribution of atomic energies shows the energetic effects of slip, including non-linear displacements in and near the core, and the elastic field further away. The EDM atomic energies agree well with anisotropic elasticity predictions in the elastic region, while they deviate in the core region due to failure of linear elasticity, and the energy deviation quantifies the core widths. Dislocation line energies are obtained by partial sums of the atomic energies within distance $r$ of the dislocation center; the core energy is extracted from the large $r$ behavior. We compare our results with an EAM and a GAP potential, showing that while both potentials produce core structures similar to DFT predictions, the GAP potential has a closer match with DFT and EDM in core energies.