A theoretical study of electronic and vibrational properties of neutral, cationic, and anionic B₂₄ clusters

Abstract

ABSTRACT:The equilibrium geometries, electronic and vibrational properties, and static polarizability of B 24 , B 24 Ϫ , and B 24 ϩ clusters are reported here. First-principles calculations based on density functional theory predict the staggered double-ring configuration to be the ground state for B 24 , B 24 Ϫ , and B 24 ϩ , in contrast to the quasi-planar structure observed in small neutral and ionized B n clusters with n Յ 15. Furthermore, the (4 ϫ B 6 ) tubular structure is found to be relatively stable in comparison to the 3D cage structure. The presence of delocalized and multicentered bonds appears to be the cause of the stability of the double-ring and tubular isomers. For the ground state of B 24 , the lower and upper bound of the electron affinity is 2.67 and 2.81 eV, respectively, and the vertical ionization potential is 6.88 eV. Analysis of the frequency spectrum of the double-ring and tubular isomers reveals the characteristic vibrational modes typically observed in carbon nanotubes. The corresponding IR spectrum also reflects the presence of some of these characteristic modes in the neutral and ionized B 24 , suggesting that double-ring and tubular structures can be considered as the building blocks of boron nanotubes.

Stability and Electronic Properties of Atomistically-Engineered 2D Boron Sheets

“…The flat {1212} sheet has a 6-fold coordination of boron atoms, which is uniformly repeated in a basic triangular three-atom unit. In fact, this terminology can be derived through a planar projection of Aufbau principle 4 where the motifs consisting of a pentagonal pyramidal B 6 and the hexagonal pyramidal B 7 are found to be the basic unit to form elemental boron clusters. The calculated cohesive energy of the flat {1212} sheet is 5.48 eV/atom, higher than that of the sp 2 -bonded hexagonal graphene-like boron sheet, which is only 4.96 eV/atom (Table 2).…”

First-principles study of the stability and electronic properties of sheets and nanotubes of elemental boron

“…Boron holds a unique place among the elements of the periodic table by having the most varied polymorphism, which includes quasicrystal [1] and novel nanostructures [2][3][4][5][6], in addition to the complex icosahedral networks observed in conventional boron-rich solids [7]. Based on a generalization of the Euler-Poincaré formula for a cylinder [8], it was suggested that boron nanotubes (BNTs) could be constructed by the appropriate ÔwrappingÕ of an ÔidealizedÕ triangular boron sheet, referred to as the {1 2 1 2} sheet.…”

“…a double-ring BNT fragment) with diameter $0.52 nm, can be found in (10,0) zigzag BNT, which is constructed from either the {1 2 2 1} or the {1 2 1 2} boron sheet. On the other hand, the basic unit of the most stable (6,0) zigzag type-I BNT considered in this study, with diameter $0.40 nm, can be found in B 24 [5].…”

An ab initio investigation of boron nanotube in ringlike cluster form

“…Such idea is mainly based on the fact that the DRT configuration is the most stable structure among various isomers of B 20 , B 24 , B 30 , B 36 , and B 96 clusters. [20][21][22][23] Moreover, the DRT clusters have been detected in experiments. 25 Our previous study also showed that for large sized boron clusters the three-ring tubular and DRT configuration are more stable than other ones.…”