Early stages of sintering of Si₃N₄ nanoclusters via parallel molecular dynamics

We investigate early stages of sintering of silicon nitride (Si₃N₄) nanoclusters by molecular-dynamics (MD) simulations on parallel computers. Within 100 pico seconds, an asymmetric neck is formed between nanocrystals at 2,000K. In the neck region, there are more four-fold than three-fold coordinated Si atoms. In contrast, amorphous nanoclusters develop a symmetric neck, which has nearly the same number of three-fold and four-fold coordinated Si atoms. In the case of sintering among three nanoclusters, a chain-like structure forms in 200 pico seconds. The present study shows that sintering is driven by rapid diffusion of surface atoms and cluster rearrangement.