B 12 H n and B 12 F n : planar vs icosahedral structures
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NANO EXPRESS
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B12Hn and B12Fn: planar vs icosahedral structures Nevill Gonzalez Szwacki1 and C J Tymczak2*
Abstract Using density functional theory and quantum Monte Carlo calculations, we show that B12Hn and B12Fn (n = 0 to 4) quasi-planar structures are energetically more favorable than the corresponding icosahedral clusters. Moreover, we show that the fully planar B12F6 cluster is more stable than the three-dimensional counterpart. These results open up the possibility of designing larger boron-based nanostructures starting from quasi-planar or fully planar building blocks. Background The icosahedral B 12 H 12 2- cluster is the most stable molecule among the number of polyhedral boranes synthesized so far [1]. A large-scale and efficient synthesis of fully fluorinated boron hydrides, e.g., icosahedral B12F122-, has been also reported [2]. On the other hand, the all-boron C3v-B12 cluster is quasi-planar, and it was reported to be one of the most stable all-boron clusters. It was also established by extensive computations that the quasi-planar B 12 cluster is much lower in energy than the all-boron icosahedral B 12 cluster. This was reported not only for the neutral clusters [3], but also for the charged ones [4]. It is then interesting to investigate what happens with the relative stability of the two (quasi-planar and three-dimensional (3D)) all-boron structures upon addition of hydrogen or fluorine atoms. This is the purpose of this study. Quasi-planar and 3D boron clusters with the number of hydrogen atoms smaller than the number of boron atoms have been studied both theoretically [5-11] and experimentally [12-14]. Ohishi et al. [12] reported the formation of B 12 H n + (n = 0 to 12) cationic clusters through ion-molecule reactions of the decaborane ions (B10Hn+, n = 6 to 14) with diborane molecules (B2H6) in an external quadrupole static attraction ion trap. The mass spectrum analysis revealed that among the B12Hn+ clusters with different hydrogen content n, the B12H8+ molecule was the main product. In the same study, using first principle calculations with the Becke 3-parameter Lee-Yang-Parr (B3LYP) hybrid functional and the 6-31G (d) basis set, the authors compared the relative energies * Correspondence: [email protected] 2 Department of Physics, Texas Southern University, Houston, TX, 77004, USA Full list of author information is available at the end of the article
of quasi-planar and 3D B 12H n+ clusters with n varying from 0 to 12. According to that study, two-dimensional (2D) clusters with n = 0 to 5 are energetically preferred over the 3D structures, whereas 3D clusters are energetically favored for n ≥ 6. In a more recent combined experimental/theoretical study, Ohishi et al. [14] suggested that quasi-planar B12Hn+ with n = 0 to 3 clusters can be obtained by further removal of H atoms from the decaborane ions. This opens up the possibility of changing the structure of the B 12H n + cluster by controlling the number of hydrogen atoms in the cluster. To our knowledge, there are no previou
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