Model-based computation of powder diffraction patterns for carbon nanotubes

The powder diffraction patterns of single- and multi-walled carbon nanotubes have been computed using the Debye equation including the Debye-Waller factor. The geometrical models of given diameter and chirality were constructed by generating the Cartesian coordinates of atoms. The results of such simulations are compared with the pulsed neutron diffraction data and agreement between them is regarded as criterion of validity of the model. All the features of the experimental intensity function of the multi-walled nanotubes are reproduced by the simulated powder diffraction pattern computed for the model consisting of nine coaxially stacked tubes. The Debye-Waller factor increasing with square root of the interatomic distance was used to account for decay of intensity oscillations. The two-shell and bundle models were considered to reproduce the weak first diffraction peak for the single-walled nanotubes. (C) 2003 Elsevier B.V. All rights reserved