Unusual phase transition mechanism induced by shear strain in Si₂BN planar structures and comparison with graphene:...

Using ab initio methods we show that by applying shear strain, a phase transition occurs between the AB and the AA Si₂BN planar sheets. Si-Si bonds stretch and bend towards the strain direction, causing an internal displacement of the remaining almost unchanged Si₂BN strips. As the shear strain increases, Si-Si bonds weaken and break, while leading to new Si-Si bond formation and causing the phase transition. The planar structure is maintained throughout the application of the strain, with no buckling, a phenomenon not reported so far in other 2D materials. Performing the same calculations for graphene we show that its structural deformations are strikingly different and result in buckling.