Molecular dynamics study of size effects in the compression of metallic glass nanowires

Molecular dynamics simulations have been employed to investigate the mechanical response to uniaxial compression of metallic glass nanowires with radius in the range between 1 and 6 nm. It is found that the mechanical behavior of nanowires, based on the activity of shear transformation zones, is affected by size effects. The nanowires in which the largest number of shear transformation zones involve only bulk atoms exhibit a behavior similar to that of bulk systems. When a relatively large number of shear transformation zones can also involve surface atoms, the mechanical response of the nanowire changes. It seems in particular that atomic volume effects determine the loss of correlation between consecutive atomic rearrangements. As a consequence, shear transformation zones are no longer able to exhibit an autocatalytic dynamics. The mechanical response of the nanowires with smallest radii is correspondingly different from the one of other nanowires.