Finite size effects on Raman spectrum of single-walled boron nitride nanotube

Using the spectral moments method, we present calculations of Raman active modes of Single Walled Boron Nitride Nanotube (SW-BNNT). The Spectra are computed for chiral and achiral nanotubes in terms of their diameter and length. The behaviors of low frequency Raman active modes characteristic, in terms of the tube diameter revealed that these frequencies are diameter dependent. We show that the number of Raman active modes, their frequencies, and intensities depend on the length and chirality of the nanotubes. These predictions are useful to interpret the experimental Raman spectra of BNNTs.Using the spectral moments method, we present calculations of Raman active modes of Single Walled Boron Nitride Nanotube (SW-BNNT). The Spectra are computed for chiral and achiral nanotubes in terms of their diameter and length. The behaviors of low frequency Raman active modes characteristic, in terms of the tube diameter revealed that these frequencies are diameter dependent. We show that the number of Raman active modes, their frequencies, and intensities depend on the length and chirality of the nanotubes. These predictions are useful to interpret the experimental Raman spectra of BNNTs

Nonresonant Raman Spectrum Of Boron Doped Single Walled Carbon Nanotubes

In the present work, We use a force constant model to study the vibrationnel modes of boron doped single walled carbon nanotubes. This model is used to calculate the nonresonant Raman spectra of these nanomaterials in the framework of bond-polarisation theory by using either direct diagonalisation of the dynamical matrix or the spectral moments method. The effect of substitution of carbon by boron atoms shows that the higher Raman frequency region is dominated by a broad bond whereas the lower one is characterized by a shift of radial bonds.In the present work, We use a force constant model to study the vibrationnel modes of boron doped single walled carbon nanotubes. This model is used to calculate the nonresonant Raman spectra of these nanomaterials in the framework of bond-polarisation theory by using either direct diagonalisation of the dynamical matrix or the spectral moments method. The effect of substitution of carbon by boron atoms shows that the higher Raman frequency region is dominated by a broad bond whereas the lower one is characterized by a shift of radial bonds

Raman active modes in single-walled boron nitride nanotube bundles

We use the spectral moments method in the framework of the bond-polarization theory to calculate polarized nonresonant Raman spectra of chiral and achiral bundles of single walled boron nitride nanotubes (BWBNNTs) as a function of their diameter and chirality. The Spectra are computed for infinite size of BWBNNTs. We used a Lennard-Jones potential to describe the van der waals intertube interactions between tubes in a bundle. We show that the Raman active modes in the low wave number region are very sensitive to the nanotube diameter. We found that for infinite nanotube bundles, additional Radial Breathing Like mode appears in the low wave number region. These results are useful to interpret the experimental Raman spectra of BWBNNTs

FILLING RATE DEPENDENCE ON THEORETICAL RAMAN SPECTRA OF CARBON C 60 PEAPODS

International audienceWe use the spectral moments method in the framework of the bond-polarization theory to calculate nonresonant Raman spectra of C60 peapods as a function of the concentration of fullerenes inside the single wall carbon nanotubes. The evolution of the average Raman intensity ratios between Raman mode of C 60 molecules and nanotube as a function of the concentration of fullerenes has been analyzed and a general good agreement is found between calculations and measurements

Raman spectrum of single-walled boron nitride nanotube

International audienceUsing the spectral moments method, the calculations of the Raman spectra of single-walled boron nitride nanotubes (SW-BNNTs) were performed in the framework of the force constants model. Spectra were computed for chiral and achiral nanotubes for different diameters and lengths. The Raman scattering intensities were determined using the bond-polarizability model and a good agreement with group theory analysis was found. We show that the modes in the low frequency region are very sensitive to the nanotube diameter variation, whereas the ones associated to the tangential region are chirality dependent. The number of Raman active modes, their frequencies, and intensities depend on the length of the nanotube. (C) 2009 Elsevier B.V. All rights reserved

Raman spectra of carbon nanowires made of single walled carbon nanotubes encasing polyynes

In this work, the Raman spectra of LCCs encapsulated single-walled carbon nanotubes (SWCNTs) are calculated using the spectral moment’s method. To derive the optimum configurations of the linear carbon chains inside nanotubes, the minimum energy calculations using a convenient Lennard-Jones expression of the van der Waals intermolecular potential is devoted. The optimized structures show that the minima correspond to nanotubes configurations with diameter close to 0.68nm. The influence of the nanotube diameter and chirality are investigated. We also address the important question of the effect of filling degree using the frequency of Raman active modes. These predictions are useful to interpret the experimental data

Raman-Active Modes in Finite and Infinite Double-Walled Boron Nitride Nanotubes

International audienceIn this theoretical work, we study the Raman spectra of double-walled boron nitride nanotubes (DBNNTs) as a function of their diameters, chiralities, and lengths. Calculations are performed using the spectral moments method coupled to the bond polarizability model. This original approach allows us to consider not only infinite tubes as usual in most theoretical models but also tubes with finite lengths. We provide benchmark theoretical data to estimate thediameter and length of DBNNTs using Raman measurements

Tube-Length Dependence on Theoretical Raman Spectra of Single-Walled BC3 Nanotubes and Bundle Size Effect

International audiencePolarized Raman spectra of single-walled BC3 nanotubes(SBCNTs) are calculated as a function of their diameter, chirality, length,and bundle size using a classical force field combined with the bondpolarizabilitymodel. For isolated infinite tubes, we give a mathematicalmodel to estimate their diameter from their Raman spectra. Thetangential modes are sensitive to the tube chirality. The length shorteningof the tube below ∼50 nm leads to the appearance of several additionalRaman lines in the regions of breathing modes and tangential modes. ForSBCNT bundles, the position of the radial breathing mode is significantlyupshifted with respect to its position in isolated SBCNTs, and a specificbundle breathing-like mode is observed below 300 cm−1

Size effects on the infrared responses of boron carbide nanotubes

International audienceThe spectral moment's method combined with a force constant model is used to calculate the polarized infrared spectra in single-walled BC3 nanotubes. We discuss the evolution of these spectra as a function of the diameter, chirality and length of nanotubes. Our work provides benchmark theoretical data for the assignment of experimental infrared spectra