In Situ Solid‐State Generation of (BN)2‐Pyrenes and Electroluminescent Devices

New BN‐heterocyclic compounds have been found to undergo double arene photoelimination, forming rare yellow fluorescent BN‐pyrenes that contain two B? N units. Most significant is the discovery that the double arene elimination can also be driven by excitons generated electrically within electroluminescent (EL) devices, enabling the in situ solid‐state conversion of BN‐heterocycles to BN‐pyrenes and the use of BN‐pyrenes as emitters for EL devices. The in situ exciton‐driven elimination (EDE) phenomenon has also been observed for other BN‐heterocycles.     

Electronic,optical, and mechanical properties of BN,AlN, and InN with zinc-blende structure under pressure

In this work, the electronic, optical, and mechanical properties of BN, AlN, and InN under the action of pressure are calculated. For each of these compounds, the energy band structure, band gaps(E~L_g, E~Γ_g, E~X_g), refractive index(n),dielectric constants(ε_∞, ε_0), elastic constants(C_11, C_12, C_44), and relevant parameters such as bulk(B_u), shear(S_h), and Young's(Y_0) moduli are studied, and other important parameters such as bond-stretching(α), bond-bending(β) force constant, internal-strain parameter(ζ), effective charges(e~*_T, Z~*), anisotropy factor(I_s), Poisson's ratio(P_o), Cauchy ratio(C_a), the ductility index(μ_D), and linear compressibility(C0_) are also calculated. The effects of pressure on all studied properties are investigated. Our results are in good agreement with the available experimental and theoretical data for BN,AlN, and InN.     

掺杂B_nN_n(n=12,16,20,24,28)团簇的生成热

中等尺寸的硼氮富勒烯笼与碳笼富勒烯相似,具有纳米尺度的球形内包空间,应该可以形成内包原子的笼状包合物,且无论从理论研究,还是从应用研究上讲都还处于起步阶段.我们采用第一性原理方法计算了第一、二、三、四周期内各元素原子作为M原子,分别构建M@B_nN_n(n=12,16,20)包合物并计算结合能.发现当硼氮富勒烯笼直径较小时,不同元素结合能的大小规律与原子半径的规律相符.副族元素的Mn、Fe、Co和Ni较其它元素的包合物稳定性明显增加.     

Analyse von synthetischem Bornitrid durch Elektronenbeugung

Ohne Zusammenfassung

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Analysis of synthetic boron nitride by electron diffraction

     

Spin-polarized zero-energy states in BN/C core–shell quantum dots

Boron-nitride (BN) domains in graphene or graphene domains in BN monolayer offer additional freedoms for tuning the electronic properties of these BN/C nanostructures, which is quite crucial for the applications in nanoscale devices. Based on first-principles calculations combined with a simple Hubbard model, we show that the electron zero-energy states (ZESs) of BN/graphene core–shell quantum dots (QDs) in triangular shapes can be well tuned by varying the size and topology of each domain. The net spin of the systems is dominated by the graphene segment which can be described by a Lieb?s theorem. We also demonstrated that a π-electron Hubbard model within a mean-field approximation is implementable in dealing with the electron spin-polarization of BN/C hetero-structured graphene-like materials. This provides an efficient theoretical approach for the BN/C systems where electron spin-polarization is involved.     

温度、应变率和空位缺陷对氮化硼纳米管压缩性能的影响

采用分子动力学方法,分别模拟了完好的和含有缺陷的氮化硼纳米管的轴向压缩过程。原子间的相互作用采用Tersoff多体势函数来描述。结果表明,同尺寸的锯齿型氮化硼纳米管的临界轴向压缩强度高于扶手型氮化硼纳米管,这与碳纳米管的研究结果一致。发现纳米管的压缩强度,如临界轴向内力在低温下受温度影响明显,并且和应变率的大小有关。然而,应变率对纳米管的弹性变形没有影响。另外,还发现空位缺陷降低了纳米管的力学性能。与完好的纳米管相比,含有缺陷的纳米管轴向压缩强度对于温度的影响并不敏感。     

Aromaticity of Heterofullerenes C18BxNy (x+y=2) and Their Molecular Ions

The aromaticity of all possible substituted fullerene isomers of C18N2, C18B2, C18BN, and their molecularions which originate from the C20 (Ih) cage were studied by the topological resonance energy (TRE) and the percentage topological resonance energy methods. The relationship between the aromaticity of C18BxNy isomers and the sites where the heteroatoms dope at the C20 (Ih) cage is discussed. Calculation results show that at the neutral and cationic states all the isomers are predicted to be antiaromatic with negative TREs, but their polyvalent anions are predicted to be aromatic with positive TREs. The most stable isomer is formed by heteroatom doping at the 1,11-sites in C18N2, C18B2, and C18BN. Heterofullerenes are more aromatic than C20. The stability order in the neutral states is C18N2>C18BN>C18B2>C20. The stability order in closed-shell is C18B2 8->C20 6->C18BN6->C18N2 4-. This predicts theoretically that their polyvalent anions have high aromaticity.     

Adsorption sensitivity of pristine and Al- or Si-doped boron nitride nanoflake to COCl2: a DFT study

ABSTRACT

The adsorption of phosgene (COCl₂) on pristine, Al- and Si-doped boron nitride nanoflakes (BNNFs) is studied using density functional theory calculations. The adsorption energies of the most stable complexes, formed from interaction between COCl₂ and the pristine, Al- and Si-doped BNNFs are ?28.97, ?78.71 and ?171.60?kJ/mol at the M06-2X/6-31?+?G* level of theory, respectively. It is found that COCl₂ experiences a chemisorption interaction over the doped BNNFs, significantly altering its structure with respect to the gas-phase molecule. The COCl₂ adsorption can also induce a change in the HOMO–LUMO or SOMO–LUMO energy gap of the surface. In particular, the adsorption of COCl₂ is found to decrease the HOMO–LUMO energy gap of Al-doped BNNF by about 30%. It is suggested that the Al- or Si-doped BNNFs can be considered as a potential material for detecting toxic COCl₂.