  Tension-compression asymmetry is a notable feature of plasticity in bcc
single crystals. Recent experiments reveal striking differences in the
plasticity of bcc nanopillars for tension and compression. Here we present
results from molecular dynamics simulations of nanopillars of bcc Fe in tension
and compression. We find that a totally different deformation mechanism applies
in each cases: dislocation glide in compression and twinning in tension. This
difference explains experimentally-observed asymmetry in the nanopillar
morphology.
