* Corresponding author. Fax: 33-(0)4-76-48-39-06. E-mail address: rols@ill.fr (S. Rols) Physica B 276}278 (2000) 276}277 Structure and dynamics of single-wall-carbon nanotubes probed by neutron scattering S. Rols*, E. Anglaret, J.-L. Sauvajol, G. Coddens, H. Schober, A.-J. Dianoux Institut Laue-Langevin, BP 156, F-38042 Grenoble, Cedex 9, France Groupe de Dynamique des Phases Condense & es, Universite & Montpellier II, France Laboratoire Le & on Brillouin, CE-Saclay, F-91191 Gif-sur-Yvette, France Abstract Elastic and inelastic neutron scattering were used to study the structure and dynamics of single-wall-carbon nanotubes (SWNT) self-assembled into nanobundles (NBSWNT). Calculations on "nite-size bundles were compared to the neutron di!raction data and time-of-#ight (TOF) neutron scattering measurements are discussed in the light of molecular dynamics calculations on isolated SWNT.  2000 Elsevier Science B.V. All rights reserved. Keywords: Carbon nanotubes; Inelastic neutron scattering; Di!raction A single-wall-carbon nanotube can be described as a graphene sheet rolled up into a cylindrical tube. They are unique 1D systems self-organized into 2 D limited- size crystals, usually called nanobundles of SWNT. Most of their physical properties, including mechanical, optical and transport, are known to depend on their molecular structures and bundle-like crystalline packing [1]. It is therefore of primary importance to study the structural and dynamical properties of the NBSWNT in order to achieve a better understanding of the intertube interac- tions and of the intercalation processes inside the bundles. The dotted curve of Fig. 1 represents the result of a typical neutron di!raction (ND) measurement of an SWNT raw sample synthesised by the electric arc tech- nique [2]. This signal is corrected from the impurities contributions generally present in the samples [3]. The low-Q part is the di!raction signature of the bi- dimensional hexagonal packing of the tubes in the bundles. The most intense peak, located at 0.45 A s  corresponds to the (1 0) Bragg re#ections on this 2 D ar- ray [1,2]. Three other Bragg re#ections are observed below 1.5 A s . In order to get an accurate descrip- tion of the structure, we have performed calculations of the di!raction pattern of NBSWNT based on a phase separation model [4,5]. Account was taken for the "nite size of the bundles D  and for the diameter distribution of the tubes in the modelised sample. The latter was considered to be a Gaussian function centered on a diameter D  with a standard deviation . Such calculations were successfully compared to di!raction data of various SWNT samples [3}5]. Such a good agreement is also found for D  "13.6 A s , "1A s (FWHM"1.7 A s ) with 19 tubes per bundles for this sample (Fig. 1 line). In Fig. 2 we present the "rst TOF measurement of the GDOS of a puri"ed SWNT sample (Fig. 2a dots) com- pared with that of graphite (Fig. 2b), and a theoretical one calculated from a force constant model for an iso- lated tube with a diameter of 16.3 A s (Fig. 2a line) [1,3,6]. Compared to graphite, additional DOS is observed in the NBSWNT sample in the 17}24 meV range. This excess of DOS is attributed to the radial breathing modes (RBM) contributions at the  point of the "rst Brillouin zone. The main di!erences between the experimental data and the calculation are found below 15 meV. They may be due to the presence of intertubes external modes. Calculation of the GDOS on NBSWNT including the 0921-4526/00/$ - see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 5 2 6 ( 9 9 ) 0 1 4 8 4 - 2