The role of higher-symmetry phases in anisotropy of theoretical tensile strength of metals and intermetallics

Fully self-consistent ab initio electronic structure calculation of the the oretical tensile strength of single-crystalline tungsten and NiAl loaded un iaxially along [001] and [111] directions is performed using the full-poten tial LAPW method. Although tungsten is elastically nearly isotropic (C-44 a pproximate to C'), theoretical tensile strength exhibits a marked anisotrop y. Similarly, in NiAl, the 'hard' orientation [001] differs very significan tly from the [111] orientation. This anisotropy is explained in terms of hi gher-symmetry structures present or absent along the deformation paths.