N Sukumar - Electronic Origin of the Stability of Transition Metal Doped B14 Drum Shaped Boron Clusters and Their Assembly in to a Nanotube

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      Publication Details (including relevant citation   information):

      J. Phys. Chem. C, Publication Date (Web): January   27, 2017
      DOI: 10.1021/acs.jpcc.6b10838


      We study the stability of drum-shaped transition metal (TM) doped   boron clusters, M@Bn with n = 14 and 16, and M = 3d, 4d, and 5d   TM atom using ab initio calculations. Our results show that   drum-shaped M@B14 clusters are favored for M = Cr, Mn, Fe, Co,   and Ni, while in other cases, open conical or bowl shaped   structures become more favorable. The isoelectronic Ni@B14 and   Co@B14- clusters have large highest occupied molecular   orbital-lowest unoccupied molecular orbital (****-LUMO) gaps and   these are magic clusters. Their stability has been correlated   with the occurrence of magic behavior with 24 valence electrons   in a disk jellium model while for Fe@B14 case, the drum structure   is deformed and the stability occurs at 22 delocalized valence   electrons. The bonding nature in these clusters has been studied   by analyzing the electron density at bond and ring critical   points, the Laplacian distribution of the electron density, the   electron localization function, the source function, and electron   localization-delocalization indices, all of which suggest two and   three-center σ bonding within and between the two B7 rings,   respectively, and hybridization between the TM d orbitals and the   π bonded molecular orbitals of the drum. The infrared and Raman   spectra of these magic clusters show all real frequencies,   suggesting the dynamical stability of the drum-shaped structures.   There is a low frequency mode associated with the M atom. Results   of the electronic spectra of the anion clusters are also   presented that may help to identify these species in future   experiments. Further, we discuss the stability of 24 delocalized   valence electron systems Mn@B16 anion, Fe@B16, Co@B16 cation, and   other related clusters. Assembly of Co@B14 clusters has been   shown to stabilize a carbon nanotube-like nanotube of boron with   Co atomic nanowire inside while a nanotube of boron with   triangular network has been obtained with the assembly of Fe@B16   drum-shaped clusters. Both the nanotubes are metallic.

      Address (URL): http://pubs.acs.org/doi/abs/10.1021/acs.jpcc.6b10838