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The elastic properties of boron nitride nanotubes have been calculated using the Tersoff–Brenner potential which is a bond order potential used successfully previously for carbon nanotubes. In the present calculation, the same form of potential is used with adjusted parameters for hexagonal boron nitride. The Young’s modulus and shear modulus for single-walled armchair and zigzag tubes of different radii have been calculated. The effects of tube diameter are investigated. The computational results show the variation of Young’s modulus and shear modulus of boron nitride nanotubes with nanotube diameter. The results have been compared with available data, experimental as well as calculated.

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Augmented growth of MWCNT-primed wheat, enhancement in grain number, biomass, stomatal density, xylem-phloem size, epidermal cells, and water uptake is observed while finding no DNA damage. This opens up an entirely new aspect to using cost-effective nanomaterials (the MWCNTs were produced in-house) for enhancing the performance of crop plants. © 2017 Society of Chemical Industry.

Ab initio investigation of structural, electronic and vibrational properties of nitrogen-doped fullerenes (C(60-n)Nn, for n = 1-12) has been performed using numerical atomic orbital density functional theory. We have obtained the ground-state structures for C(60-n)Nn for n = 1-12, which show higher stability with a single nitrogen in a pentagon and two nonadjacent nitrogen atoms in a hexagon. Nitrogen doping leads to structural deformation, with the diameter showing variation from (7.14 - 0.24) to (7.14 + 0.10) A. The average diameter of C(60-n)Nn shows a small decrease for n > or = 5, with a minimum value of 7.06 A for n = 12. The change in the average diameter signifies the volume contraction, which is also maximum for C48N12. The binding energy per atom is found to decrease as a function of the number of N atoms. The HOMO-LUMO gap is found to decrease with an increase in substitutional nitrogen atoms; however, no systematic pattern could be observed. The Mulliken charge analysis performed on all optimized geometries shows a charge transfer of -0.3 to -0.45 (or 0.3-0.45 electrons) from nitrogen to carbon atoms, resulting in nitrogen atoms behaving as electrophilic sites. The harmonic vibrational frequency analysis shows the absence of any imaginary mode. The vibrational frequencies are found to decrease with an increase in the number of nitrogen atoms in C(60-n)Nn. The results obtained are consistent with available theoretical and experimental results.

Modification induced by 110 MeV Ni ion irradiated thin film samples of C 60 on Si and quartz substrates were studied at various fluences. The pristine and irradiated samples were investigated using Raman spectroscopy, electrical conductivity and optical absorption spectroscopy. The Raman data and band gap measurements indicate that swift ions at low fluences result in formations that involve multiple molecular units like dimer or polymer. High fluence irradiation resulted in sub-molecular formations and amorphous semiconducting carbon, indicating overall damage of the fullerene molecules. These sub-molecular units have been identified with nanocrystalline diamond and nanocrystalline graphite like formations. INTRODUCTIONEver since its synthesization in the laboratory 1 , the fullerene solid has been a subject of significant interest as target for ion-beam irradiation. The interest was stimulated by the potential of fullerene material towards superconductivity by implanting foreign ions in the fullerene cage and other applications like optical limiters, electrical storage devices, C 60 based diodes and transistors etc. Irradiation effects of keV and some MeV energies has been investigated [2][3][4][5][6][7][8][9][10][11][12][13][14] . In general, it has been observed by various research groups that the C 60 materials undergo heavy damage by low energy ion irradiation in the energy range 30 -300 keV of various ions [2][3][4][5][6] . There has also been study on irradiation effects of MeV energies on fullerene films [7][8][9][12][13][14] . Itoh et al 7 have reported fragmentation of C 60 induced by impacts of 2 MeV Si 4+ ions. T.Le.Brun et al 8 have reported ionization and fragmentation in C 60 molecules by impacts of Xe ions in the energy range of 420 -625 MeV. Subsequently 9 , there has been some interest in studying the phase transformations of the C 60 solids using MeV energies. It has been reported that under suitable conditions of temperature and pressure, the C 60 undergoes a dimer or a polymeric phase transformation 10,11 . Ion beam irradiation could provide similar conditions so that the formation of aggregates (of molecules of C 60 ) is favoured. This could further result in the formation of solids of these aggregates. The energy of the ions and their fluence play a key role in the end product of the target.Energetic ions loose energy during their passage in a material. The strength of interaction of the incident ion in a material i.e., with the electrons of the atoms in the target material (including the core electrons of the constituent atoms or molecules) as well as with the nuclei 2 (which happen to be the mass centers) depends on the mass, charge and energy of the incident ion. Therefore, it is of interest to study the interaction of ion beams with fullerene solids using swift ions at various fluences. The interaction of the incident ion with the atomic radii (or molecular mass center) is an elastic collision process and is prominent at low energy (eV to few hundred keV). On the other hand the intera...

The magnetic properties of 3d transition metals (TM) encapsulated inside smaller fullerenes ranging from C20 to C36 have been investigated using spin polarized density functional theory. The TM impurities stabilize asymmetrically at an off-center position for n≥28. The total magnetic moment (MM) of TM@Cn complexes are largely contributed by TMs and a small amount of MM of 0.12-0.50 μB is induced on the cage carbon atoms. The 3d TM atoms interact with C atoms of C20 and C28 cage ferromagnetically (FM) except for Ni@C28 which shows antiferromagnetic (AFM) interaction. The magnetic interactions change from FM to AFM in C32 cage for Ti, V, Cr and Mn. The MM gets quenched in Ni@Cn for n≥32. The total MM of Mn@Cn does not show any change although the nature of magnetic interactions changes from FM to AFM at n=32. Ti and V are the only TMs which show positive cohesive energy in all fullerenes considered. The smallest fullerene which can encapsulate all 3d TM are Cn for n≥32, consistent with available experimental and theoretical results.

Carbon nanotubes (CNTs) are being used for varied applications. It is therefore important to study their stability under extreme conditions of temperature and irradiation. In this work, we report the stability of CNTs [both single-wall CNTs (SWCNTs) and multiwalled CNTs (MWCNTs)] under irradiation of a carbon ion beam of energy 55 MeV. The irradiated samples were analyzed using Raman spectroscopy. The Raman results indicate the interesting phenomenon of healing or annealing of CNTs under ion beam irradiation. The annealing process appears to begin at the lowest value of fluences and persists for quite a good range of fluence values. As the irradiation dose increases (≈1×1014 ions/cm2) the MWCNTs begin to amorphize whereas the SWCNTs system continues to heal.