Ab initio density functional investigation of B_24 cluster: Rings, Tubes, Planes, and Cages

We investigate the equilibrium geometries and the systematics of bonding in various isomers of a 24-atom boron cluster using Born-Oppenheimer molecular dynamics within the framework of density functional theory. The isomers studied are the rings, the convex and the quasiplanar structures, the tubes and, the closed structures. A staggered double-ring is found to be the most stable structure amongst the isomers studied. Our calculations reveal that a 24-atom boron cluster does form closed 3-d structures. All isomers show staggered arrangement of nearest neighbor atoms. Such a staggering facilitates $sp^2$ hybridization in boron cluster. A polarization of bonds between the peripheral atoms in the ring and the planar isomers is also seen. Finally, we discuss the fusion of two boron icosahedra. We find that the fusion occurs when the distance between the two icosahedra is less than a critical distance of about 6.5a.u.Comment: 8 pages, 9 figures in jpeg format Editorially approved for publication in Phys. Rev.

Novel spherical boron clusters and structural transition from 2D quasi-planar structures to 3D double-rings

Based on ab initio quantum-chemical and density functional methods we determined the geometry, electronic and structural properties of three cluster-families: boron spheres, double-rings and quasi-planars up to a cluster size of 122 atoms. The most stable structure is the B100 sphere showing similar shape but more stability than the B80 cage recently proposed by Yakobson et al [PRL 98, 166804 (2007)]. In addition we compared the stability of the three cluster families to each other, and reported the structural transition from 2D quasiplanar clusters to 3D double-rings. This transition occurs between the B16 and B19 clusters

Ionization energies, Coulomb explosion, fragmentation, geometric, and electronic structures of multicharged boron clusters B(n) (n=2-13)

Based on the ab initio quantum chemical methods, we have determined fragmentation channels, ionization energies, and the Coulomb explosion of multicharged boron clusters B(n) (n = 2-13), where n is the cluster size. The electron-deficient boron clusters sustain more stability and hardly fragment when they are negatively charged. Stability of boron clusters decreases with increasing ionization. Only by the first ionization the odd-size clusters are more stable than the even-size clusters. Further ionizations cause the repulsive Coulomb force between the constituent atoms to get stronger, and lead first to metastable states, then to the Coulomb explosion of clusters. None of the cationic boron clusters studied remain stable after six times ionization. The critical charge for metastability is estimated as Q(m) <= n/2 for even-size clusters, and Q(m) <= 1/2 (n - 1) for odd-size clusters. In addition, the critical charge for the Coulomb explosion is found to be Q(c) = n/2 + 1 for even-size clusters, and Q(c) = 1/2(n + 1) for odd-size clusters. Relative stability of clusters with respect to their nearest neighbors is determined from the analysis of their second energy difference data. Several dissociation channels of B(n)(+) and B(13)(Q) isomers with the lowest fragmentation energies are presented. All of the vibrational frequencies are found positive indicating that no transition state is possible for the clusters studied. Reliability of our data is verified with a good agreement with experimental results

Search for the largest two-dimensional aggregates of boron: An ab initio study

We use ab initio density functional calculations to investigate the structural stability and vibrational spectra of small boron aggregates in different charge states. In search of candidates for the largest stable 2D boron aggregates, we focus on systems with one atom less than B-20 clusters with confirmed 3D geometry. Whereas the most stable structural isomer of B-19(-) is two-dimensional, in agreement with experimental results of Huang et al. [Nat. Chem. 2, 202 (2010)], the second most stable anionic and the most stable neutral and cationic species form a 3D pyramidal structure that had been missed previously

Fragmentation and Coulomb explosion of multicharged small boron clusters

We extensively study the fragmentation and Coulomb explosion of multiply charged small boron clusters B-n (n = 2-13), where n is the cluster size. Our calculations are based on ab initio quantum-chemistry methods. Highly charged unstable clusters dissociate spontaneously into several neutral or charged fragments, and large amounts of energy are produced, depending on the charge of the parent cluster. We argue that this mechanism makes boron clusters a clean, safe, and cheap energetic material

Metal-like electrical conductance in boron fullerenes

Electron transport properties of B-fullerenes, B 80 and B 100, are investigated with the use of the first-principles density functional theory (DFT), in conjunction with the Landauer-Büttiker formalism and compared with C-fullerene, C 60, under similar conditions. The differential conductance and the tunnel current for B-fullerenes sandwiched between Au contacts are calculated to be much higher than those for C 60. An analysis of the calculated density of states and frontier orbitals suggests such a behavior of B-fullerenes to result from metallike states, formed from the hybridization of Au 6s orbital with the highest occupied molecular orbital of B-fullerenes delocalized over the equator of the icosahedral cages, generally absent in Au-C 60-Au complex. Due to their enhanced electron transport properties, B-fullerenes appear to be attractive candidates for future nanoscale electronics. © 2010 American Chemical Society

Electron transport in boron fullerenes

The electron transport properties of B80 fullerene is studied using first-principles density functional theory in conjunction with the Landauer-Büttiker quantum transport formalism. The electron transmission in B80 fullerene is calculated to be much higher than that in C 60 fullerene in the Fermi-level region. The enhanced transmission in the B80 fullerene is attributed to its spatially extended charge distribution in delocalized bonds. © 2008 IEEE