Possible mechanism of BN fullerene formation from a boron cluster: Density‐functional tight‐binding molecular dynamics simulations

We simulate the formation of a BN fullerene from an amorphous B cluster at 2000 K by quantum mechanical molecular dynamics based on the density‐functional tight‐binding method. We run 30 trajectories 200 ps in length, where N atoms are supplied around the target cluster, which is initially an amorphous B₃₆ cluster. Most of the incident N atoms are promptly incorporated into the target cluster to form B‐N‐B bridges or NB₃ pyramidal local substructures. BN fullerene formation is initiated by alternating BN ring condensation. Spontaneous atomic rearrangement and N₂ dissociation lead to the construction of an sp² single‐shelled structure, during which the BN cluster undergoes a transition from a liquid‐like to a solid‐like state. Continual atomic rearrangement and sporadic N₂ dissociation decrease the number of defective rings in the BN cluster and increase the number of six‐membered rings, forming a more regular shell structure. The number of four‐membered rings tends to remain constant, and contributes to more ordered isolated‐tetragon‐rule ring placement. © 2016 Wiley Periodicals, Inc.