Moiré-of-Moiré phases formed in twisted graphene/hexagonal boron nitride heterostructures under high pressure

Abstract

The atomistic behavior and mechanical properties of twisted graphene/h-BN (T-GBN) heterostructures under hydrostatic high-pressure is investigated using density functional theory with the Perdew–Burke–Ernzerhof functional. Systematic explorations of T-GBN heterostructures with different twist angles (9.43°, 13.17°, and 21.78° characterized by moiré patterns) reveal that stable phases, denoted as Moiré-BC₂N (m-BC₂N), are formed. Notably, the m-BC₂N (21.78°) phase maintains perfect sp³ hybridization, even upon complete relaxation to zero pressure, and its mechanical stability is confirmed; comprehensive mechanical evaluations unveil the crystal anisotropic attributes, further highlighting its exceptionally high hardness. Specifically, m-BC₂N (21.78°) demonstrates an impressive hardness of 74.7 GPa. Furthermore, electronic structure analysis of m-BC₂N exhibits wide bandgaps (E_g), , comparable to diamond, while m-BC₂N (9.43°) exhibits a lower bandgap, . This study sheds light on designing novel BCN ternary structures with outstanding mechanical properties under high pressures.