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

Abstract

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.

Investigation of size effects on the structure of liquid GeSe2 calculated via first-principles molecular dynamics

“…[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] Very large simulation boxes have been adopted to monitor the onset of such effects. [27][28][29][30][31][32][33][34][35] However, we are not aware of a DFT-FPMD study in which the results pertaining to two sizes of the simulation cell (of about 100 and 500 atoms) have been compared at the same level of statistical accuracy, i.e., by exploiting time trajectories of comparable lengths. This is exactly the purpose of our paper, devoted to the production of a new, complementary set of data on liquid GeSe 2 , obtained with a periodic simulation cell containing N = 480 atoms.…”

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

“…Significant amount of research is being performed to understand the deformation mechanisms in MGs and to develop compositions and processing strategies to mitigate the brittle failure [5][6][7][8][9][10]. Due to the inherent small spatial dimensions of shear transformation zones (STZs, groups of a few to a few tens of atoms) and shear bands (extended shear layers of tens of nanometer thickness)-the two basic deformation units in MGs, nanoscale MGs are frequently employed in both experimental and computational studies [11][12][13][14][15][16][17][18][19]. While these studies have provided useful insights into, for example, how testing conditions or sample imperfections (e.g.…”

Metallic glasses : thermal, mechanical properties and their correlation

“…Regarding the computational technique, it is superior to the experimental technique in the sense that it can capture the electronic/atomic structures and relate them to the physical properties of bulk systems. Recently, Delogu [78], who performed the molecular dynamics of uniaxial compression on a binary MG, proposed a new insight into the size effect on the deformation behavior, exactly on the activity of STZs. He suggested that as the sample size is reduced so that a relatively large number of STZs consists of surface atoms as well, the autocatalytic activation of STZs is no longer operable because of the loss of the excess free volume on the surface.…”