Strain-Mediated Modification of Phagraphene Dirac Cones

A first-principles study on the electronic and dynamical properties of phagraphene [Nano Lett. 2015, 15 (9), p 6182] is presented. This carbon allotrope exhibits a square unit cell, Dirac cones, and robustness against uniaxial deformation. By analyzing the contribution of each carbon atom orbital in the formation of the electronic states, we conclude that only the p(z) orbitals of 8 out of the 20 atoms in the square unit cell are responsible of the formation of the nanostructure Dirac cones. Spatial symmetry breaking of the underlying honeycomb-like network upon shear stress application leads to a band gap opening. The analysis of the phonon spectra demonstrates that the dynamical stability of phagraphene is guaranteed for small distortion angles. Phagraphene is identified here as the first all-C graphitic monolayer with Dirac cones modifiable by a small and realistic physical deformation. The analysis and conclusions of this study can be applied to other monolayered materials exhibiting Dirac cones in square lattices.