Influence of Boundary Conditions on the Structural Evolution of Hexagonal Boron Nitride upon Heating

Abstract

Introduction: In this study, we investigate how boundary conditions influence the structural evolution of hexagonal boron nitride (h-BN) under thermal stress. Specifically, we analyze two configurations: a zigzag h-BN nanoribbon (ZBNNR) and an in-plane graphene/h-BN/graphene (g/h-BN/g) heterostructure, focusing on the role of graphene layers in modulating h-BN's behavior during heating.

Methods: Molecular dynamics simulations were employed to simulate thermal effects on the ZBNNR and hybrid g/h-BN/g heterostructure. These simulations tracked structural changes, bond dynamics, and phase transitions across varying temperatures to assess boundary-driven modifications in h-BN stability.

Results: Both systems exhibited first-order phase transitions. The melting temperature of ZBNNR was 3800 K, significantly lower than the 6150 K observed for the g/h-BN/g heterostructure. At melting, B–B and N–N bonds in ZBNNR contracted, whereas these bonds remained stable in the heterostructure. Coordination analysis revealed that 5.9% of atoms in ZBNNR retained a coordination number of three, compared to only 2.6% in the h-BN layer of the heterostructure, highlighting graphene’s stabilizing effect.

Conclusion: The presence of graphene layers in the hybrid heterostructure substantially enhances the thermal stability of h-BN, elevating its melting temperature and suppressing bond distortion. This work underscores the critical role of boundary conditions in tailoring nanoscale material properties for high-temperature applications.