The ideal tensile strengths of the $\mathrm{B}2$-type $\left(\mathrm{CsCl}\right)$ transition-metal aluminides $\mathrm{FeAl}$, $\mathrm{CoAl}$, and $\mathrm{NiAl}$ have been investigated using an ab initio electronic structure total energy method. The three materials exhibit dissimilar mechanical behaviors under the simulated ideal tensile tests along [001], [110], and [111] directions. $\mathrm{FeAl}$ is weakest in tension along [001] whereas CoAl and NiAl are strongest in the same direction. The weakness of $\mathrm{FeAl}$ along [001] direction is attributed to the instability introduced by the filling of antibonding $d$ states.

• Received 12 May 2004

DOI:https://doi.org/10.1103/PhysRevB.70.054107