Prediction of three-dimensional stretchable boron nitride nanoribbons

In this paper, a series of fully sp(2)-hybrid three-dimensional boron nitride nanoribbons (3D-BNNRs) polymorphs entirely composed of hexagonal rings is described herein. The 3D-BNNRs can be considered as connected BNNRs with different widths. All the predicted structures are thermodynamically metastable with 0.111-0.281 eV per BN unit higher than hBN. The elastic constants and phonon dispersion calculations show the 3D-BNNRs are mechanically and dynamically stable. The 3D-BNNRs are semiconductors, which are independent of the width of BNNRs. Tensile strength calculations show the 3D-BNNRs are very strong in the BNNRs-like plane, comparable to graphene and BNNRs. Moreover, under uniaxial strains, the 3D-BNNRs are very stretchable, and can hold more deformation along the direction perpendicular to BNNRs motif than in other directions, although the ideal strengths are lower than those in-plane direction.