pss basic solid state physics b status solidi www.pss-b.com physica REPRINT Curvature effects in the D * band of small diameter carbon nanotubes J. Kürti 1 , V. Zólyomi 1, 2 , J. Koltai 1 , F. Simon 3, 4 , R. Pfeiffer 4 , and H. Kuzmany 4 1 Department of Biological Physics, Eötvös University, Pázmány Péter sétány 1/A, 1117 Budapest, Hungary 2 Research Institute for Solid State Physics and Optics of the Hungarian Academy of Sciences, P.O. Box 49, 1525 Budapest, Hungary 3 Budapest University of Technology and Economics, Institute of Physics and Condensed Matter Research Group of the Hungarian Academy of Sciences, 1521 Budapest, P.O. Box 91, Hungary 4 Fakultät für Physik, Universität Wien, Strudlhofgasse 4, 1090 Wien, Austria Received 18 June 2007, revised 20 June 2007, accepted 20 June 2007 Published online 2 October 2007 PACS 63.22.– m, 78.30.Na, 78.67.Ch The energy dispersion of the D * (G′) band shows a strong diameter dependence according to Raman measurements on double walled carbon nanotubes. The Raman shift of the small diameter inner tubes shows an average softening. There is an oscillation around an average linear behavior with slopes of 108 cm –1 /eV and 61 cm –1 /eV for the outer and inner tubes, respectively. We show that the experimental observation can be reproduced by simple model calculations if the curvature effects are taken into ac- count. The phonon softening with increasing curvature was proven by first principles calculations. phys. stat. sol. (b) 244, No. 11, 4261 – 4264 (2007) / DOI 10.1002/pssb.200776168