Can Hydrogen Catalyze Transitions between h-BN and c-BN in Volume Plasma?

In a range of temperatures from 1500 to 2500 K, processes of transformation between various nanometer-scale boron nitride structures in the presence of hydrogen are simulated. We find that hydrogen catalyzes the transition from the sp(2) hybridization of B and N atoms in hexagonal boron nitride (h-BN) to sp(3) hybridization, creating tetrahedral amorphous boron nitride (ta-BN) or cubic boron nitride (c-BN), at 1500 and 2000 K, respectively. At 2000 K in the presence of hydrogen, ta-BN can evolve to c-BN, usually partially encapsulated by a h-BN cage. All of these transformational processes of boron nitrides have analogs in graphene-diamond conversions. Change of atom hybridization can also proceed in the opposite direction under different conditions. Using quantum-classical molecular dynamics based on the density functional tight-binding method, we analyze the evolution of the nanoscale particles via the hybridization state of B/N atoms, ring composition, exchange of particles with environment, as well as the energetics of the processes. The simulations allow the estimation of temperature windows favorable for stable h-BN, c-BN, and amorphous BN when interacting with hydrogen.