First-principles total-energy calculations for planar shear and cleavage decohesion processes in B2-ordered NiAl and FeAl

The fracture and deformation behavior of the ordered NiAl and FeAl intermetallics were studied on the basis of full-potential local-density linear-muffin-tin orbital total-energy calculations of the shear and cleavage decohesion processes. Based on ab initio calculations of generalized stacking fault energetics, the structure of the dislocation core was constructed in the scope of the Peierls-Nabarro model with a generalized restoring force law. We found that dislocations in FeAl show a strong tendency for splitting into two superpartials, in contrast with NiAl. Estimates of the Peierls stress yield the correct preferred slip systems for NiAl (i.e., <100> {110}) and FeAl (i.e., <111> {110}).