Mechanical Properties of Amorphous Silicon Nanoparticles

The compression of amorphous silicon nanoparticles is investigated by means of molecular dynamics simulations, at two temperatures and for diameters equal to 16 and 34 nm. The nanoparticles deform plastically, with maximum contact stresses in the range 8.5-11 GPa, corresponding to strains between 12 and 24%. No clear size effect is observed. Despite large contact stress values, the formation of high-density crystalline or amorphous phases is not observed, presumably due to the presence of lateral free surfaces allowing for plasticity deconfinement. Atomic displacements analysis confirms that during plastic deformation, atoms close to indenters are first pushed towards the nanoparticle center, before migrating laterally towards free surfaces. Plastic deformation leads to an increase of fivefold coordinated atoms, which are spatially correlated with the largest atomic displacements.