Mechanical properties of hydrogen-passivated silicon and silicon carbide nanoparticles

Abstract Unlike the perfect models often used in numerical simulations, real nanoparticles are usually characterized by an oxidized or passivated surface, whose the effect on mechanical properties is not well known. In the present work we perform first principles molecular dynamics calculations to simulate the flat punch compression of small hydrogen passivated silicon and silicon carbide nanoparticles. They reveal that the nanoparticles yield at high strains and preferentially by amorphization. Small rotations are often observed before yielding. Our investigations suggest that these rotations are favored by the
presence of the hydrogen passivated layer. Another consequence is a notable reduction of stiffness, due to the lower bending strength of Si/C-H bonds compared to the compression strength of the Si/C lattice. At last it is found that the amorphization of silicon carbide is facilitated by the presence of the hydrogen passivated layer.