Generalized-stacking-fault energy and dislocation properties inbccFe:  A first-principles study

By using an ultrasoft pseudopotentials method based on the density-functional theory, we have calculated the generalized stacking fault (GSF) energies for the [100](110), [001̄](110), and [11̄1](110) slip systems in bcc Fe within the local density approximation (LDA), spin-polarized LDA (LSDA), generalized gradient approximation (GGA), and spin-polarized GGA (SGGA). LSDA and SGGA give much higher unstable stacking fault energies than LDA and GGA. Our results show that GSF energy is sensitive to the spin state of the system. A spin-polarized calculation should be considered for the slip systems such as [11̄1](110). From the obtained GSF energy curves, we also demonstrate the edge dislocation properties of [100](010), [001̄](110), and 1/2[11̄1](110) within the framework of the Peierls-Nabarro model. It shows that the spin-polarized calculations give a narrower dislocation core width, higher unstable stacking fault energy, and larger maximum restoring stress as compared with the non-spin-polarized calculations.