S. Dmitrović

Electro-optical properties of single-walled carbon nanotubes

Abstract Optical conductivity tensor and electron energy loss function for individual single-wall carbon nanotubes (SWCNT) of arbitrary chirality are found. The reported two types of results obtained in the TEM measurements on the isolated SWCNT of the same diameter are interpreted. The difference in plasmon excitation probabilities is shown to be related to the different numbers of allowed interband transitions in the chiral and achiral tubes, while the peak position shift is to be attributed to the interrelationship between the parities of the electronic states of the armchair tubes and the polarization of the perturbing field.

Mechanical coupling in homogeneously deformed single-wall carbon nanotubes.

We developed a full symmetry implementing method, based on classical molecular dynamics with the Brenner-Tersoff potential, for determining the optimal configuration of homogeneously deformed infinitely long single-wall carbon nanotubes. All nanotubes with diameter less than 1.3 nm are studied. Systematic analysis of the coupling between different types of deformation shows that, in the tubes with chiral angle close to zero and 30°, the torsion-induced circumferential strain is opposite to the induced axial strain. Also, torsion in zigzag tubes induces larger circumferential strain, but in armchair tubes it yields a larger axial strain. The influence of diameter on axial-stretching-induced torsion becomes significant only for narrow tubes. Finally, significant deviation from the linear dependence of axial-strain-induced radial deformation is found for zigzag tubes. The presented results are important for the calculation of electro-optical properties of nanotubes under strain.

Raman spectra of commensurate double-walled carbon nanotubes

Using nonresonant bond-polarization theory, Raman spectra of periodic double-walled carbon nanotubes are calculated. Although the symmetry of these tubes is highly reduced in comparison with the symmetry of the layers, the intensities of Raman active modes do not show significant changes. In ZZ polarization, modes related to radial breathing and high energy modes of individual layers remain the most intensive ones, even though the number of totally symmetric modes could be quite high. The shift of all Raman active modes with notable intensity is discussed and special attention is given to the possibility of tube identification from Raman data. In the case of breathing-like modes, the frequency of the out of phase mode is found to be chirality dependent, while the in phase one remains only diameter dependent as in the case of individual layers.

Extremely compact formulas for the Fourier transform of a product of two-centre Slater-type orbitals

A compact formula for the Fourier transform of a product of Slater-type orbitals on different centres is derived. The integral is reduced to a finite one-dimensional integration over non-oscillatory hypergeometric functions of type . The formula is valid for all quantum numbers and does not involve the reduced Bessel functions that are usually used to evaluate these integrals. Reduced formulas are calculated for some special directions in the reciprocal space. Also, some useful identities for the Fourier transforms of a product of Slater-type orbitals with correlated sets of parameters are obtained. In order to illustrate simple and efficient use of the presented results, we have applied them to graphene.

Raman Spectra Of Double‐Walled Carbon Nanotubes

Using nonresonant bond‐polarization theory, Raman spectra of periodic double‐walled carbon nanotubes (DWCNTs) are calculated. Due to the lower symmetry of DWCNT, the number of Raman active modes is much larger compared to those of its layers. Complete frequency range of the tubes spectra has been analyzed for large number of tubes. We found that only modes whose frequencies are below 800 cm−1 have noticeable up shifts compared to those of isolated layers. Special attention is given to radial breathing modes (RBMs) and G‐band region since these modes are used for the identification of singe‐walled carbon nanotubes. In case of breathing like modes (BLMs), frequency of the out of phase mode is found to be chirality dependent, while the in phase one remains only diameter dependent as in the case of individual layers.