Quantum Manifestations of Graphene Edge Stress and Edge Instability*

We have performed first-principles calculations of graphene edge stresses, which display two interesting quantum manifestations absent from the classical interpretation: the armchair edge stress oscillates with nanoribbon width and the zigzag edge stress is noticeably reduced by spin polarization [1]. Such quantum stress effects in turn manifest in mechanical edge twisting and warping instability, showing features not to be captured by empirical potentials or continuum theory. Edge adsorption of H and Stone-Wales reconstruction are shown to provide alternative mechanisms in relieving the edge compression and hence to stabilize the planar edge structure. We also demonstrate that the quantum manifestation of mechanical properties such as stress to exist generally in many low-dimensional nanostructures, such as BN system. [1] Huang et al., Phys. Rev. Lett. 102, 166404 (2009).