Magnetic properties of C-N planar structures: d(0) ferromagnetism and half-metallicity.

We investigate, from first principles calculations, the magnetic properties of planar carbon nitride structures with the lowest formation energies within twenty eight distinct stoichiometries and porosities. Surprisingly, we find that 3/4 of the low-energy carbon nitride structures present energetically favorable magnetic phases, and that more than 3/10 are ferromagnetic. This suggests that d(0) magnetism is a usual feature in this class of materials. Notably, within the energetically favorable ferromagnetic structures, we find that two structures have very high stabilization energies for ferromagnetic order, one having the highest predicted so far for this class of materials. We also find that several structures are half-metals, and one structure is half-zero-gap semiconductor (semicondutor in one spin channel, and graphene-like in the other channel).

Non-hexagonal-ring defects and structures induced by healing and strain in graphene and functionalized graphene.

We perform ab initio calculations for the strain-induced formation of non-hexagonal-ring defects in graphene, graphane (hydrogen-functionalized graphene) and graphenol (hydroxyl-functionalized graphene). We find that the simplest of such topological defects, the Stone-Wales defect, acts as a seed for strain-induced dissociation and multiplication of topological defects. Through the application of inhomogeneous deformations to graphene, graphane and graphenol with varying initial concentrations of pentagonal and heptagonal rings and small-sized voids, we obtain several novel stable structures that possess, at the same time, large concentrations of non-hexagonal rings (from fourfold to elevenfold) and small formation energies.