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Band Gaps and Optical Spectra of Halogenated and Hydrogenated Graphenes

Salle de séminaire de l’IRSAMC Bât 3R1b4 3ième étage portes N325 et 327

Séminaire de Frantisek Karlicky (Ostrava University)

New two-dimensional materials derived from graphene by attachment of hydrogen and halogens have attracted considerable interest over the past few years because of their potential applications (e.g., in electronic devices) [1]. Here, we consider the effect of electron-electron and electron-hole correlation on the electronic/optical properties of materials under study. Especially, large difference between the experimental optical gap and the electronic band gap from many-body GW theory for fluorographene [2,3] is explained by unusual large binding energies of excitons obtained by solution of Bethe-Salpeter equation (BSE), whereas point defects lower band gaps and absorption energies only slightly [4]. Similar effects are predicted for double-layer fluorographene and graphite fluoride [5]. Moreover, we found huge excitonic effect in recently prepared hydrogenated and fluorinated graphenes, called fluorographanes CFH [6] – the effect is larger than in pure graphane CH or pure fluorographene CF. Finally, we show the importance of careful computational setup for reliable usage of many-body GW and BSE methods.

[1] Karlicky F., Datta KKR., Otyepka M., Zboril R., ACS Nano 7 (2013) 6434
[2] Nair RR., Novoselov KS., Geim AK., et al. Small 6 (2010) 2877
[3] Zboril R., Karlicky F., Bourlinos AB., et al., Small 6 (2010) 2885
[4] Karlicky F., Otyepka M., J. Chem. Theory Comput. 9 (2013) 4155
[5] Karlicky F., Otyepka M., Ann. Phys. 526 (2014) 408
[6] Sofer Z., Simek P., Mazanek V., et al., Chem. Commun. 51 (2015) 5633