Stability of disclinations in carbon monolayer

We apply first-principles calculations to study the stability of carbon structures with disclinations of angles θ=±π3. Nanocones and saddle-like compounds are investigated. It is shown that a layer with negative disclination is more stable than its converse. We have also investigated the effect of introducting boron or nitrogen as substitutional impurity in carbon nanosaddles. Nitrogen, out and on the defect, is shown to increase the formation energy, while boron, on heptagon, lowers the energy for formation of the heptagonal defect. In addition, we have found that such structures display spin polarization.