Structure and Stability of Boron Nitrides: The Crossover between Rings and Cages

Effect of substitution on the bonding in He dimer confined within dodecahedrane: A computational study

The effect of substitution in the dodecahedrane (C₂₀ H₂₀ ) cage on bonding in the confined He dimer is analyzed. The HeHe distances inside the halogenated dodecahedrane C₂₀ X₂₀ (X = FBr) cages are found to be less than half of that in the free He dimer. Comparing the equilibrium structure of He₂ @C₂₀ H₂₀ with He₂ @C₂₀ X₂₀ at ωB97XD/def2-TZVPP level, it is found that the He-He distances are relatively larger in the latter cases indicating the influence of halogen groups on the interaction between the cage and the trapped He pair. The viability of the He₂ @C₂₀ X₂₀ complexes is reflected in the presence of a very high activation energy barrier against the thermochemically feasible dissociation process producing free He₂ and C₂₀ X₂₀ . Quantum theory of atoms in molecules (QTAIM) approach reveals a partial covalent interaction between He pair.

Non-equilibrium steady state conductivity in cyclo[18]carbon and its boron nitride analogue

A ring-shaped carbon allotrope was recently synthesized for the first time, reinvigorating theoretical interest in this class of molecules.

Influence of the adsorption of toxic agents on the optical and electronic properties of B12N12 fullerene in the presence and absence of an external electric field

The interaction energies and optoelectronic properties of sarin (SF) and chlorosarin (SC) on the B₁₂N₁₂ with and without the presence of an electric field have been studied using density functional theory (DFT) calculations.

Structure and Stability of B10N14: Cages, Sheets, and Rings

Boron nitride is a material similar to carbon in its ability to adopt numerous molecular forms, including two-dimensional sheets and three-dimensional cages and nanotubes. Boron nitride single molecules, such as B12N12, have isomeric forms that include rings and sheets, as well as cage forms analogous and isoelectronic to the carbon fullerenes. Such cages tend to be composed of squares and hexagons to allow perfect alternation of boron and nitrogen atoms, which is possible because of the 1 : 1 ratio of boron-to-nitrogen atoms. What about molecules in which this 1 : 1 ratio does not apply? In the current study, theoretical calculations are carried out on molecules of B10N14 to determine energetically favorable isomers. Density functional theory is used in conjunction with Dunning basis sets. Cage, sheet, and ring isomers are considered. Energetic trends are calculated and discussed, in comparison to comparable studies on B12N12.

A comparative study of the CO oxidation reaction over pristine and C-doped boron nitride fullerene

In this work, we employ density functional theory calculations to investigate the CO oxidation mechanisms over B₁₂N₁₂ and B₁₁N₁₂C nanocages.

Boron-nitride and aluminum-nitride "Pringles" and flapping motion

Motivated by the recent successful synthesis of a new nanocarbon, namely, a warped, double-concave graphene "Pringle" (Nat. Chem., 2013, 5, 739), we investigate properties of warped boron-nitride (BN) and aluminum-nitride (AlN) analogues, i.e., the non-planar B40N40H30 and Al40N40H30 "Pringles" using density functional theory (DFT) calculations. Particular attention is placed on the effect of non-hexagonal rings on the stability and physical properties of BN and AlN Pringles. We find that the warped BN and AlN Pringles with one pentagon and five heptagons are stable without imaginary frequencies. Both the warped B40N40H30 and Al40N40H30 Pringles are expected to be flexible in solution as both can periodically change their shape in a dynamic "flapping" fashion due to their much lower activation barrier of racemization compared to that of the C80H30 counterpart. Since the warped B40N40H30 possesses a smaller HOMO-LUMO gap than the planar B39N39H30, it is expected that incorporating non-hexagonal ring defects by design can be an effective way to modify electronic properties of BN-based nanoplates.

A new generation of B(n)N(n) rings as a supplement to boron nitride tubes and cages

In B(n)N(n) cages or tubes, when the quasi-borazine rings are attached to each other through a pair of common atoms of B and N, the bonding structure is named class A. On the other hand, there are some B(n)N(n) rings including a covalent bond between two atoms of B and N, which are named class B. In all previous studies, both reports of synthesis and theoretical calculation of boron nitride tubes and cages, the quasi-borazine units are attached together like class A. There are no theoretical or experimental reports from class B compounds except for a brief study in our previous works (Struct. Chem. 2012, 23, 551-580; J. Phys. Chem. C 2010, 114, 15315.). In this study, we have used two kinds of boron nitride rings from a twisted BN sheet in the same chirality created by different mechanisms. For (4, 4) chirality, the molecules B(16)N(16) and B(15)N(15) are found to respectively represent class A and B, and for (5, 5) chirality the molecules B(20)N(20) and B(18)N(18) are respectively again of class A and B. The structure of class A rings is similar to boron nitride tubes, but we have shown that it is impossible to produce a macromolecule of class B form as tubes or cages, because there is much more instability and intermolecular tension in macro forms of class B. This is the main reason that the class B molecules are rare and, because of their small size, have not yet been synthesized, although we have some suggestions for the synthesis of these kinds of molecules. The stability and electromagnetic properties with hybrid density functional theory using the EPR-III and EPR-II basis sets for explanation of hyperfine parameters and spin densities, electrical potential, and isotropic Fermi coupling constant of these rings have been studied by the nonbonded interaction models. Normal mode analyses including aromaticity have been investigated by using the nucleus independent chemical shift values at the ring center. Interaction energy and gain in energy aid in describing the stability that is promoted upon gradual binding with molecular hydrogen, and a linear relationship occurred between them.

An all-purpose building block: B12N12 fullerene

We have theoretically shown that the boron nitride fullerene cage B(12)N(12) is an all-purpose building block for fabricating multifarious BN nanotubes. Firstly, we investigated the stability and structural of the boron nitride fullerene cage B(12)N(12) and the polymerized derivatives obtained from it. Interestingly we found out that two B(12)N(12) cages can spontaneously form one BN nanotube with two closed ends through the structural transformation when one cage meets another. These results indicated that the fullerene B(12)N(12) can be polymerized to build various remarkable polymers through the spontaneous structural transformation when they are together, which all have planer or tridimensional shapes with a hollow tubular structure, even at the juncture of the coalesced B(12)N(12). Simultaneously, after the structure optimization, the quadrangles at the juncture of the coalesced B(12)N(12) disappear to form a perfect surface only composed of hexagons. Then, we calculated the energy of all the considered nanostructures. The polymerization of the fullerene B(12)N(12) is exothermic and thus can form very stable derivative polymers. These theoretical conclusions stimulate us to use the fullerene B(12)N(12) as an all-purpose building block to construct various BN nanostructures for purpose of fundamental research and potential applications.

Bonding analysis and stability on alternant B16N16 cage and its dimers

Bonding analysis is performed on alternant B(16)N(16) cage based on a combined study of DFT with NBO method. The main feature of such analysis is the separation of bonding structure into two components: sigma skeleton and pi bond system. Each component is further decomposed into contributions from various NBOs, thus we obtain the details of bonding interactions of every BN unit. Based on these results, relative stability of four covalent dimers of B(16)N(16) is predicted and this prediction is verified by DFT calculations. So the possibility of forecasting properties of oligomers just from analysis on monomer is highlighted in this way.

Time-Dependent Density Functional Theoretical Study of the Absorption Properties of BN-Substituted C60Fullerenes

Time-dependent density functional theoretical calculations using the B3LYP functional and 6-31G* basis set for a series of BN-substituted C60 fullerenes reveal that, unlike C60, these molecules would absorb in the visible region and that the optical and electronic properties of fullerenes can be fine-tuned with proper BN substitution.

Photoabsorption spectra of boron nitride fullerenelike structures

Optical absorption spectra have been calculated for a series of boron nitride fullerenelike cage structures BnNn of sizes n=12-36. The method used is a real-time, real-space implementation of the time-dependent density-functional theory, involving the full time propagation of the time-dependent Kohn-Sham equations. The spectra are found to be a possible tool for distinguishing between different boron nitride fullerene species and isomers. The trends and differences in the spectra are found to be related to the general geometry of the molecules. Comparison between local-density and generalized-gradient approximations for electron exchange-correlation functionals shows that both of them produce essentially the same spectral characteristics.

Theoretical Nitrogen NMR Chemical Shifts in Octahedral Boron Nitride Cages

We have calculated the geometrical structure, relative stability, and nitrogen chemical shifts of five boron nitride hollow octahedral cages using density functional theory. Our results show three typical ranges for nitrogen chemical shifts corresponding to each of the nonequivalent magnetic sites of the N atoms. The principal component of the electric field gradient tensor at each 14N site in boron nitride cages is predicted to be much smaller than the corresponding value in borazine, which should reflect in sharper spectral lines and much better resolution.

Boron nitride cages from B12N12 to B36N36: square-hexagon alternants vs boron nitride tubes

The structures and stabilities of square-hexagon alternant boron nitrides (Bx Nx , x=12-36) vs their tube isomers containing octagons, decagons and dodecagons have been computed at the B3LYP density functional level of theory with the correlation-consistent cc-pVDZ basis set of Dunning. It is found that octagonal B20N20 and B24N24 tube structures are more stable than their square-hexagon alternants by 18.6 and 2.4 kcal mol(-1), respectively, while the square-hexagon alternants of other cages are more stable. Trends in stability as a function of cluster size are discussed.