Multi-radical ground state and magnetism of neutral, charged and chemically
modified zigzag edged graphene nanopatches
Michael R Philpott
Center for Computational Materials Science, Institute of Materials Research,
Tohoku University, 2-1-1 Katahira, Aoba-ku, 980-8577 Sendai, Japan
Visiting Scholar, Pitzer Theory Center, Department of Chemistry, UC Berkeley,
CA 94720-1460, USA
Lundi 20 septembre 2010,
11h00 Salle RAPHAEL 2&3
site d Ivry-sur-Seine
All valence electron density functional theory (DFT) calculations of large
compact polycyclic aromatic hydrocarbon (PAH) molecules predict an interior
that approximates graphene (single sheet of graphite) [1-6]. In high symmetry
molecules the graphene core relegates spin and edge vs. interior geometry
changes to the outer (about 2) carbon rows. For example, the ground state of
the zigzag edged hexagonal shaped PAH with formula C600H60
(hex 10-zzg) is predicted to be a singlet hexa-radical with one spin
associated with each of
six sectors. Evidence comes from: (i) singlet ground state, triplet and higher
spin states of the series C6m**2H6m (m = 2, 3, 4, .. 10; hex m-zzg);
(ii) charged and/or chemically modified hex 9-zzg and 10-zzg systems;
(iii) comparisons with the linear acenes C4m+2H2m+4 (m = 9, 10) that have
similar edges but no graphene interior. The spin patterns, calculated for
these hex m-zzg molecules, provide guidance in predicting the magnetism of
arbitrary graphene nanopatches. Calculations were performed on the CCMS-IMR
Supercomputer.
References:
1) M.R.Philpott, F.Cimpoesu,Y.Kawazoe, Mat.Trans. (Jpn) 49, 2448(2008)
2) M.R.Philpott, F.Cimpoesu, Y.Kawazoe, Chem. Phys.354, 1(2008)
3) M.R.Philpott, Y.Kawazoe, Chem.Phys.358, 85(2009)
4) M.R.Philpott, Y.Kawazoe, Phys. Rev. B 79, 233303(2009)
5) M.R.Philpott, Y. Kawazoe, J.Chem.Phys.131,0214706(2009)
6) M.R.Philpott, S.Vukovic,Y.Kawazoe, W.A.Lester Jr, J.Chem.Phys.133,044708(2010)