Ab initio analysis of theoretical isotropic strength and elasticity of nickel aluminide compounds

The influence of chemical composition on the elastic response of NixAly under isotropic deformation is theoretically studied in terms of crystal energetics. Pure Ni, Ni3Al, NiAl, NiAl3 and pure Al crystals were selected as representative NixAly compounds. The total energy is computed by means of two ab initio approaches. Elastic moduli and equilibrium atomic volumes are determined and the crystal stability is analyzed at the inflection point of the dependence of the total energy on the volume. The isotropic theoretical tensile strength is evaluated using the stability analysis. All calculated values agree well with the available experimental data. The only exceptions are the overestimated values of the NiAl shear moduli.