Supplementary Information Tuning the Properties of Graphene by a Reversible Gas-Phase Reaction
Download 1.57 Mb.
|
Fig. S7. Relative energies and magnetic moments per unit cell of different configurations of the methylated and hydrogenated SLG. As shown in this figure, we examine the relative energies and magnetic moments per unit cell of the three configurations with fixed methyl and hydrogen concentration. It shows that the most energetically favorable conformer is that hydrogen absorbs at the para-position of the methyl, while the conformer of hydrogen at meta-position of the methyl has the highest energy. This is because the ortho-position absorption will induce larger distortion and the meta-position absorbed conformer is magnetic7. We then examined the electronic properties of this methylated SLG. The calculated band structure and partial density of states (PDOS) are shown in Fig. S8. The system is found to be nonmagnetic with an indirect band gap of 3.63 eV around the Fermi level, which is comparable with that of graphane (3.50 eV with a direct band gap)8. The PDOS shows that the gap is mainly dominated by the 2p orbitals of the C atoms. In order to examine it in detail, we plotted wave functions of the highest valence band (HVB) and the lowest conductance band (LCB). We can see that both of them are contributed by the C atoms of SLG; the HVB has delocalized π character while the LCB has localized π* character. We then anticipate that the band gap of SLG can be modulated in a large range under different coverages. 
Fig. S8. Band structure (right), PDOS (middle) and wave functions of frontier bands (left) for the methylated SLG. Finally, we considered the mechanical property of the methylated SLG. A rectangle unit cell is used to calculate the elastic constant C along x and y directions. The elastic constant can be written as  where  and  are deformation energy and lattice constant along α (= x and y) directions, respectively. The total energy variation with respect to unit cell deformation is plotted in Fig. S9, where we can deduce the values of Cx (326.6 N/m) and Cy (419.9 N/m), respectively. These values are comparable to the average experimental elastic modulus of 342 N/m in pristine graphene sheet9 but they are larger than those of graphdiyne (158.57 and 144.90 N/m)10.
Fig. S9. Total energy variation per unit cell with respect lattice deformation along x and y directions. The curves are the parabola fitting. 1. Ferrari, A.C. et al. Raman spectrum of graphene and graphene layers. Phys. Rev. Lett. 97, 187401 (2006). 2. Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865 (1996). 3. Kresse, G. & Furthmuller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54, 11169-11186 (1996). 4. Kresse, G. & Joubert, J. From ultrasoft pseudopotentials to the projector augmented-wave method. Phys. Rev. B 59, 1758-1775 (1999). 5. Monkhorst, H. J. & Pack, J. D. Special points for Brillouin-zone integrations. Phys. Rev. B 13, 5188-5192 (1976). 6. Zhou, J., Wang, Q., Sun, Q., Chne, X. S., Kawazoe, Y. & Jena, P. Ferromagnetism in semihydrogenated graphene sheet. Nano Lett. 9, 3867-3870 (2009). 7. Zhou, J., Wang, Q., Sun, Q., Chne, X. S., Kawazoe, Y. & Jena, P. Ferromagnetism in semihydrogenated graphene sheet. Nano Lett. 9, 3867-3870 (2009). 8. Sofo, J. O., Chaudhari, A. S. & Barber, G. D. Graphane: A two-dimensional hydrocarbon. Phys. Rev. B 75, 153401 (2007). 9. Lee, C., Wei, X., Kysar, J. W. & Hone, J. Measurement of the elastic properties and intrinsic strength of monolayer graphene. Science 321, 385-388 (2008). 10. Long, M., Tang, L., Wang, D., Li, Y. L. & Shuai, Z. G. Electronic structure and carrier mobility in graphdiyne sheet and nanoribbons: Theoretical predictions. ACS Nano 5, 2593-2600 (2011). Directory: journal journal -> Version: 17 October 2016 journal -> Supplementary Methods journal -> El Niño-Southern Oscillation and the seasonal predictability of tropical cyclones journal -> Hurricanes and Global Warming An Alternative Point of View by journal -> Supplemental Material Materials and Methods journal -> Trees publication Series B, Research Report n journal -> Brown ribbon, its shiny surface spinning, a neon crimson bead the size of an insect eye journal -> Education university of Missouri journal -> Version: 05 January 2017 Download 1.57 Mb. Share with your friends:
|