Nanotube boron

TOWARDS NANOSTRUCTURED MATERIALS AN EXAMPLE OF BORON NANOTUBES... 

In order to calculate the band structure and the density of states (DOS) of periodic unit cells of a-rhombohedral boron (Fig. la) and of boron nanotubes (Fig. 3a), we applied the VASP package [27], an ab initio density functional code, using plane-waves basis sets and ultrasoft pseudopotentials. The electron-electron interaction was treated within the local density approximation (LDA) with the Geperley-Alder exchange-correlation functional [28]. The kinetic-energy cutoff used for the plane-wave expansion of... 

The results of calculations are summarized in Table 3.1. Let us note main features that are revealed. First, the concentration of B atoms in all 3D boron modifications (four crystalline and one amorphous) is almost the same (1.23-1.37) x 10 cm-. Second, the concentration of boron atoms in certain boron compounds can be comparable (e.g., BjOj) to that in structures of el ental boron or even exceed it (e.g., layered BN). This result once again underlines the effect of large voids in 3D boron structures. Third, the concentration of atoms in bundles of smaU-diameter boron nanotubes is expected to be higher than in solid-state structures, near the limit achievable in hypothetical close-packed crystal. These estimates imply that physical-technical parameters of boron-containing materials designed for neutron shielding should be evaluated in the range n = (1-25) x cm-. ... 

Chkhartishvih, L. 2009b. On quasi-classical estimations of boron nanotubes ground-state parameters. J. Phys. Conf Ser. 176 012013(9). 

Gindnlyte, A., W. N. Lipscomb, and L. Massa. 1998. Proposed boron nanotubes. Inorg. Chem. 37 6544. 

Quandt, A. and I. Boustani. 2005. Boron nanotubes. Chem. Phys. Chem. 6 2001-2008. 

Another suggested nanomaterial for use as a BNCT agent is the boron nanotube (BNT)." Boron nanotubes are one of a series of boron nanostmcmres, such as nanoribbons" and nanowires, ° that have recently been synthesized. 

The first successful synthesis of a single-wall boron nanotube was achieved by the reaction of BCI3 and H2 over an Mg-MCM-41 catalyst." The nanotubes had diameters of 3 nm and lengths of 16 nm. Unfortunately, the materials were quite sensitive to high-energy electron beams and hence detailed stmcmral characteristics... 

Carbon boron duality Lipscomb and co-workers proposed boron nanotubes, one year after our prediction. They claimed that boron nanotubes can be derived from the dual geometries of boron and carbon cylinders (nanotubes) and based upon Euler-Poincare formula for a cylinder P F=E P for vertices, Ffor faces, and E for edges). The boron duals may be imagined as arising from a correspondence between a boron atom and the center of each carbon face in the carbon nanotube. If the formula for a given carbon nanotube is taken to be C/>, then the formula for its boron dual nanotube is Bp Hp. This means that the numbers P and F are interchanged in going from carbon nanotube to boron nanotube partner. 

Fig. 16 Armchair and zigzag boron nanotubes emerged from a-sheets. ...

Carbon nanotubes are cylindrical structures related to carbon fullerene structures. Indeed, carbon nanotube cylinders are often capped at their ends with hemispherical carbon fiillerenes, illustrating the close relation of the two types of structure. Nanotube structures are of great interest because of their mechanical and one-dimensional electrical properties [2]. In our discussion of boron nanotubes [8], the duals of carbon nanotubes, we employ a generalization of Descartes-Euler formula, viz., the Euler-Poincare formula for a cylinder,... 

Figure 7b. Carbon and boron nanotubes viewed as in Figure 7a the armchair geometry corresponding to (n,m) = (10JO).

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