Phase transitions between nanosized h-BN and c-BN catalyzed by hydrogen

Phase transformations between various nanometer scale boron-nitride structures in the presence of hydrogen were simulated using quantum-classical molecular dynamics based on the density functional tight-binding (DFTB) method. Transitions of B and N atoms from sp² hybridization (hexagonal boron-nitride, h-BN) to sp³ hybridization (tetrahedral amorphous boron-nitride, ta-BN and cubic boron-nitride, c-BN) are made possible in the temperature range from 1500 to 2500 K at ambient pressure.¹ We analyzed the evolution of the nanoscale particles via the hybridization state of B/N atoms, ring composition, particles size, internal pressure, exchange of particles with environment, as well as the energetics of the processes. The simulations allow the estimation of temperature windows and particle sizes favorable for phase transitions between h-BN, c-BN, and amorphous BN when interacting with hydrogen.

¹ Predrag Krstic and Longtao Han. J. Phys. Chem. C, (2018) 122, 936−944