First-principles calculations were used to examine various properties of fully ordered stoichiometric intermetallics having CsCl-type B2 lattices. These 2 alloys, and numerous similar compounds, were found to exhibit significant polycrystalline ductility. In some cases, this exceeded 20% in tension. The calculated bulk properties were consistent with available experimental data on lattice parameters, elastic constants and stability with respect to the B27 FeB structure. The antiphase boundary energies were large; consistent with the high degree of order in these material, and with the absence of b = <111> slip in single-crystal experiments. Unstable stacking faults, associated with b = <100> slip, were quite low; unlike the case of NiAl, where these energies exceeded those of the antiphase boundaries.

Ab initio Calculation of Bulk and Defect Properties of Ductile Rare-Earth Intermetallic Compounds. J.R.Morris, Y.Ye, Y.B.Lee, B.N.Harmon, K.A.Gschneidner, A.M.Russell: Acta Materialia, 2004, 52[16], 4849-57