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Family of boron fullerenes: general constructing schemes, electron counting rule and ab initio calculations  [PDF]
Qing-Bo Yan,Xian-Lei Sheng,Qing-Rong Zheng,Li-Zhi Zhang,Gang Su
Physics , 2008, DOI: 10.1103/PhysRevB.78.201401
Abstract: A set of general constructing schemes is unveiled to predict a large family of stable boron monoelemental, hollow fullerenes with magic numbers 32+8k (k>=0). The remarkable stabilities of these new boron fullerenes are then studied by intense ab initio calculations. An electron counting rule as well as an isolated hollow rule are proposed to readily show the high stability and the electronic bonding property, which are also revealed applicable to a number of newly predicted boron sheets and nanotubes.
Ab initio study of beryllium-decorated fullerenes for hydrogen storage  [PDF]
Hoonkyung Lee,Bing Huang,Wenhui Duan,Jisoon Ihm
Physics , 2010, DOI: 10.1063/1.3387750
Abstract: We have found that a beryllium (Be) atom on nanostructured materials with H2 molecules generates a Kubas-like dihydrogen complex [H. Lee et al. arXiv:1002.2247v1 (2010)]. Here, we investigate the feasibility of Be-decorated fullerenes for hydrogen storage using ab initio calculations. We find that the aggregation of Be atoms on pristine fullerenes is energetically preferred, resulting in the dissociation of the dihydrogen. In contrast, for boron (B)-doped fullerenes, Be atoms prefer to be individually attached to B sites of the fullerenes, and a maximum of one H2 molecule binds to each Be atom in a form of dihydrogen with a binding energy of ~0.3 eV. Our results show that individual dispersed Be-decorated B-doped fullerenes can serve as a room-temperature hydrogen storage medium.
Spin-transfer mechanism of ferromagnetism in polymerized fullerenes: $Ab initio$ calculations  [PDF]
O. E. Kvyatkovskii,I. B. Zakharova,A. L. Shelankov,T. L. Makarova
Physics , 2005, DOI: 10.1103/PhysRevB.72.214426
Abstract: A mechanism of the high temperature ferromagnetism in polymerized fullerenes is suggested. It is assumed that some of the C$_{60}$ molecules in the crystal become magnetically active due to spin and charge transfer from the paramagnetic impurities (atoms or groups), such as hydrogen, fluorine, hydroxyl group OH, amino group NH$_2$, or methyl group CH$_3$, dispersed in the fullerene matrix. The exchange interaction between the spins localized on the magnetically active fullerenes is evaluated using \textit{ab initio} calculations. The nearest neighbour and next nearest neighbour exchange interaction is found to be in the range $0.1\div 0.3 $ eV, that is, high enough to account for the room temperature ferromagnetism.
Ab initio studies of electromechanical effects in carbon nanotubes  [cached]
Alves M. Verissimo,Capaz R.B.,Koiller Belita,Artacho Emilio
Brazilian Journal of Physics , 2002,
Abstract: Carbon nanotubes have recently attracted interest for their possible applications as nanoactuators and nanoswitches, as well as possible building blocks for nanoelectronics. We present ab initio calculations for uniformly charged graphene and (11,0),(9,0) and (5,5) carbon nanotubes. We also consider the effects of polaron formation in these systems. The strain-charge coe cient is calculated and compared for both graphene and the nanotubes under study.
Transforming carbon nanotubes by silylation: An ab initio study  [PDF]
Kiseok Chang,Savas Berber,David Tomanek
Physics , 2008, DOI: 10.1103/PhysRevLett.100.236102
Abstract: We use ab initio density functional calculations to study the chemical functionalization of single-wall carbon nanotubes and graphene monolayers by silyl (SiH3) radicals and hydrogen. We find that silyl radicals form strong covalent bonds with graphene and nanotube walls, causing local structural relaxations that enhance the sp3 character of these graphitic nanostructures. Silylation transforms all carbon nanotubes into semiconductors, independent of their chirality. Calculated vibrational spectra suggest that specific frequency shifts can be used as a signature of successful silylation.
High stability of faceted nanotubes and fullerenes of multi-phase layered phosphorus: A computational study  [PDF]
Jie Guan,Zhen Zhu,David Tománek
Physics , 2014, DOI: 10.1103/PhysRevLett.113.226801
Abstract: We present a paradigm in constructing very stable, faceted nanotube and fullerene structures by laterally joining nanoribbons or patches of different planar phosphorene phases. Our ab initio density functional calculations indicate that these phases may form very stable, non-planar joints. Unlike fullerenes and nanotubes obtained by deforming a single-phase planar monolayer at substantial energy penalty, we find faceted fullerenes and nanotubes to be nearly as stable as the planar single-phase monolayers. The resulting rich variety of polymorphs allows to tune the electronic properties of phosphorene nanotubes (PNTs) and fullerenes not only by the chiral index, but also by the combination of different phosphorene phases. In selected PNTs, a metal-insulator transition may be induced by strain or changing the number of walls.
Strain energy calculations of hexagonal boron nanotubes: An ab-initio approach  [PDF]
S. K. Jain,P. Srivastava
Physics , 2013, DOI: 10.5488/CMP.16.33802
Abstract: An ab initio calculations have been carried out for examining the curvature effect of small diameter hexagonal boron nanotubes. The considered conformations of boron nanotubes are namely armchair (3,3), zigzag (5,0) and chiral (4,2), and consist of 12, 20, and 56 atoms, respectively. The strain energy is evaluated in order to examine the curvature effect. It is found that the strain energy of hexagonal BNT strongly depends upon the radius, whereas the strain energy of triangular BNTs depends on both radius and chirality.
Contact Dependence of Carrier Injection in Carbon Nanotubes: An Ab Initio Study  [PDF]
N. Nemec,D. Tomanek,G. Cuniberti
Physics , 2005, DOI: 10.1103/PhysRevLett.96.076802
Abstract: We combine ab initio density functional theory with transport calculations to provide a microscopic basis for distinguishing between good and poor metal contacts to nanotubes. Comparing Ti and Pd as examples of different contact metals, we trace back the observed superiority of Pd to the nature of the metal-nanotube hybridization. Based on large scale Landauer transport calculations, we suggest that the `optimum' metal-nanotube contact combines a weak hybridization with a large contact length between the metal and the nanotube.
Magnetic response of carbon nanotubes from ab initio calculations  [PDF]
Miguel A. L. Marques,Mayeul d'Avezac,Francesco Mauri
Physics , 2005, DOI: 10.1103/PhysRevB.73.125433
Abstract: We present {\it ab initio} calculations of the magnetic susceptibility and of the $^{13}$C chemical shift for carbon nanotubes, both isolated and in bundles. These calculations are performed using the recently proposed gauge-including projector augmented-wave approach for the calculation of magnetic response in periodic insulating systems. We have focused on the semiconducting zigzag nanotubes with diameters ranging from 0.6 to 1.6 nm. Both the susceptibility and the isotropic shift exhibit a dependence with the diameter (D) and the chirality of the tube (although this dependence is stronger for the susceptibility). The isotropic shift behaves asymptotically as $\alpha/D + 116.0$, where $\alpha$ is a different constant for each family of nanotubes. For a tube diameter of around 1.2 nm, a value normally found in experimental samples, our results are in excellent agreement with experiments. Moreover, we calculated the chemical shift of a double-wall tube. We found a diamagnetic shift of the isotropic lines corresponding to the atoms of the inner tube due to the effect of the outer tube. This shift is in good agreement with recent experiments, and can be easily explained by demagnetizing currents circulating the outer tube.
Gómez-Jeria,Juan S.; Gonzalez-Tejeda,Nelson; Soto-Morales,Francisco;
Journal of the Chilean Chemical Society , 2003, DOI: 10.4067/S0717-97072003000300017
Abstract: the aim of this work is to find a method suitable at least for obtaining the isolated molecule band structure approximated by a gaussian broadening of the discrete eigenvalues, to apply it for a first scan of bigger and more complex structures. we compared the results of several semiempirical and ab initio quantum-chemical methods to calculate the band structure of isolated c60 and c70 fullerenes. theoretical results were compared with experimental photoemission and inverse photoemission spectra. the results show that extended hückel theory is the best method of all analyzed here. it compares well with experimental results related to valence and conduction bands for fullerene but underestimates the valence-conduction band gap by about 50%. therefore, it is suitable for a first screening of fullerene-like molecules. finally, eht is employed to predict the electronic structure of several hypothetical molecules (p60o60, n70, c30n30 and n60 )
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