Generalized-stacking-fault energy surfaces for B2-MgRE (RE=Y, Dy, Pr, Tb) intermetallic compounds: Ab initio calculations

In this study, the generalized-stacking-fault energy (GSFE) surfaces for MgRE (RE=Y, Tb, Dy, Nd) intermetallics with B2-type structures have been presented using ab initio calculations. We employ the density functional theory (DFT) within generalized-gradient-approximation (GGA) and the framework of the projector augmented wave (PAW) method. Using a slab calculation, GSFE curves along 〈110〉{1 1 0} direction and 〈111〉 {1 1 0} direction have been calculated. The fitted GSFE surfaces have been obtained from the Fourier series based on the translational symmetry. To judge that our computational accuracy is reasonable, we have compared our theoretical results for B2 intermetallics YAg with the previous calculated results. In comparison with YAg, the MgRE intermetallics exhibit lower unstable stacking fault energies in the 〈111〉 direction rather than 〈001〉 direction. So the primary slip system is 〈111〉 in the {1 1 0} plane of B2-MgRE intermetallics. The superdislocation with the Burgers vector along 〈111〉 will split into two superpartials because of the lower antiphase boundary (APB) energy in the 〈111〉{1 1 0} direction.