By using first principles calculations we report a chemical doping induced gap in graphene.The structural and electronic properties of CrO 3 interacting with graphene layer are calculated using ab initio methods based on the density functional theory. The CrO 3 acts as an electron acceptor modifying the original electronic and magnetic properties of the graphene surface through a chemical adsorption. The changes induced in the electronic properties are strongly dependent of the CrO 3 adsorption site and for some sites it is possible to open a gap in the electronic band structure. Spin polarization effects are also predicted for some adsorption configurations.

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We performed a systematic investigation of the small BxNy (x+y ≤ 6) clusters using the ab initio Hartree-Fock scheme plus second-order perturbation theory. The nature of the potential energy surface extrema are analyzed through analytical total energy second derivatives. Ionization potentials, binding energies and the stability against some possible reaction mechanisms are calculated. Based on these results we propose that the growing process for these clusters is mainly due to the successive incorporation of BN molecules. A discussion of some mass spectrometry experimental results is also presented. PACS. 36.40.-c Atomic and molecular clusters -36.40.Qv Stability and fragmentation of clusters