The effect of alloying concentration x (x=0 similar to 2.2 at%) on Cauchy pressure, elastic modulus E, the shear modulus G and their ratio G/B-0 of B-2-NiAI supercells alloyed by Cr and Ce, alone or together, was calculated in the framework of Virtual Crystal Approximation (VCA) by the first-principles pseudopotential plane-wave method. Results show that the shear modulus G and elastic modulus E of B-2-NiAl alloy are significantly increased when Cr occupies the Ni atom site in B-2-NiAl crystals, while the G and E will be reduced when Ce occupies the Al atom site. With the alloying concentration increasing to 2.1 at%, the ductility of B-2-NiAl crystals can be improved with Cr occupying the Al atom site. It is worth emphasizing that the ductility of B2-NiAl crystals is improved more significantly when Ce and Cr replace Al atom site simultaneously than that alloyed by Ce or Cr alone, especially when the alloying concentration x is 2.0 at%. The calculation result herein explains the phenomenon that the room temperature ductility of B2-NiAI alloy is enhanced obviously by Cr cooperation with Ce. The electronic density of states shows that Cr atoms or Cr cooperation with Ce atoms all can weaken the hybridization effect of the main bonding peaks of Ni(d)-Ni(d) and decrease the directivity of the main bonding peaks in B2-NiAI crystal.
