Simulation of noncrystalline silicon nanoparticles: A computer experiment

The physical properties of vitreous and amorphous silicon nanoparticles containing 300, 400, and 500 atoms are investigated by the molecular dynamics method. For a limited number of degrees of freedom, the internal energy of the amorphous phase is often less than the internal energy of the vitreous phase. The structure of the central region of silicon nanoparticles is studied in detail by constructing Voronoi polyhedra, which make it possible to determine the mean length of bonds and their number. The differences between the structures of nanoparticles in the amorphous and vitreous states are determined by the differences in the distribution of angles between Si-Si bonds and the distribution of bond lengths. Local arrangements of atoms in vitreous silicon nanoparticles are characterized by larger variations in the interatomic distances. The self-diffusion coefficients determined from mean-square atomic displacements are smaller for amorphous nanoparticles due to dominant diffusion over dangling Si-Si bonds.