Dresden 2011 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 96: Focussed session: Theory and computation of electronic structure: new frontiers VIII (jointly with HL, DS)
O 96.2: Vortrag
Freitag, 18. März 2011, 11:45–12:00, TRE Phy
Electronic Excitations in Single-Wall Carbon Nanotubes: Building-Block Approach — •Ralf Hambach1,2, Christine Giorgetti1,2, Xochitl Lopez-Lozano3, and Lucia Reining1,2 — 1LSI, Ecole Polytechnique, CNRS, CEA/DSM, Palaiseau, France — 2European Theoretical Spectroscopy Facility — 3University of Texas at San Antonio, United States
Parameter-free calculations of electron energy-loss spectra for low-dimensional systems like single-wall carbon nanotubes can become numerically very demanding or even unfeasible for large diameters.
We overcome this problem by means of a building-block approach: Combining effective-medium theory and ab-initio calculations we can describe the collective excitations in nanostructures (like carbon nanotubes) starting from the microscopic polarisability of their building blocks (bulk graphite). To this end, Maxwell’s equations are solved using the full frequency- and momentum-dependent microscopic dielectric function є(q,q′,ω) of the bulk material. The latter is calculated from first principles within the random phase approximation [1].
Besides an important gain in calculation time this method allows us to analyse the loss spectra of nanostructures in terms of their normal-mode excitations. We apply the building-block approach to study angular-resolved loss spectra for graphene and single-wall carbon nanotubes and find a very good agreement with full ab-initio calculations of these systems and corresponding experiments.
[1] AbInit: www.abinit.org, DP-code: www.dp-code.org