3D surface condensation of large atomic shear strain in nanoscale metallic glasses under low uniaxial stress.

Nanoscale metallic glasses (MGs) are frequently used in experimental and computational studies to probe the deformation mechanisms in amorphous metals. Potential consequences of the significant surface to volume ratio in these extremely small materials, nevertheless, are not well understood. Here, using molecular dynamics simulations and novel selective 3D visualization, we show that significant irreversible atomic shear strain condenses on the 3D surface of these materials under low uniaxial stress, while the interior atoms are bearing much lower, mostly reversible shear strain. This is observed for various sample geometries, dimensions, strain rates and temperatures, and attributable to the correlations of atomic shear strain with atomic potential energy and coordination number. The results reveal the profound influence of the surface on the strain partitioning in nanoscale MGs across the 3D volume, critical to the initiation and continuation of plasticity.