  We have investigated the role of temperature and magnetic effects on the
stacking-fault energy (SFE) in pure austenitic iron based on Density Functional
Theory (DFT) calculations. Using the axial next-nearest-neighbor Ising (ANNNI)
model, the SFE is expanded in terms of the free energiesof bulk with
face-centered cubic (fcc), hexagonal close-packed (hcp), and double-hcp (dhcp)
structures. The free-energy calculations require the lattice constant and the
local magnetic moments at various temperatures. The earlier is obtained from
the available experimental data, while the later is calculated by accounting
for the thermal magnetic excitations using the Monte-Carlo tech- niques. Our
results demonstrate a strong dependence of the SFE on the magnetic effects in
pure iron. Moreover, we found that the SFE increases with temperature.
