60keV N2+轰击生成BN纳米结构

报道了N2+离子轰击BN固体样品过程中,弯折BN片纳米结构和笼状小BN分子的形成.高分辨透射电子显微分析表明,厚度小于13nm的BN片具有高度可弯折性,也观察到了一些直径为0.4—1.8nm,接近于B₁₂N₁₂, B₁₆ N₁₆和B₂₀₈N₂₀₈的8面体笼状物.基于束流-固体相互作用观点,讨论了这些BN纳米结构的形成原因.     

Formation of small single-layer and nested BN cages under electron irradiation of nanotubes and bulk material

12 N₁₂, B₁₆N₁₆ and B₂₈N₂₈ octahedra which were predicted to be magic clusters for the BN system from electronic structure calculations. Received: 2 March 1998     

Theoretical study on structure of boron nitride fullerenes

We propose the parameters of the Stillinger-Weber potential for hexagonal boron nitride (BN) structures. For the reliability of these parameters, the structural property of BN fullerenes is investigated. The stability of BN fullerenes increases with increasing the number of atoms, due to the reduction of the curvature effect of BN fullerenes. The structures of the relative stable fullerenes are B₁₆N₁₆, B₁₈N₁₈, B₂₂N₂₂, B₂₅N₂₅, and B₂₈N₂₈.     

Atomic and electronic structures and thermal stability of boron-nitrogen nanopeapods: B<Subscript>12</Subscript>N<Subscript>12</Subscript> fullerenes in BN nanotubes

The atomic structures, energies of formation, electronic structures, and thermal stabilities (in the temperature range T = 0–3000 K) of novel hybrid boron-nitrogen nanostructures (so-called nanopeapods B₁₂N₁₂@BN-NT) are simulated using the self-consistent density functional tight-binding (DFTB) method. The B₁₂N₁₂@BN-NT nanopeapods are regular linear ensembles of B₁₂N₁₂ boron-nitrogen fullerenes encapsulated in boron-nitrogen nanotubes (BN-NT), such as the (14, 0) nonchiral zigzag BN nanotubes, the (8, 8) nonchiral armchair BN nanotubes, and the (12, 4) chiral BN nanotubes.     

Lattice Dynamical Simulation of Guest-Host Interaction in N2 Clathrate Hydrate

We perform the lattice dynamical simulation studies of hydrate host lattice interacting with Xe, Ar, and N2 atoms/molecules. The calculated results show that the well-defined peaks （2.0meV and 3.8meV） and another peak （6.2 me V） are assigned to the vibrations of N2 molecules in large and small cages, respectively. It is confirmed that the double N2 molecule occupancies of large cage lead to filling of the mode gap between the small cage and the large cage.     

毛刺状竹节结构氮化硼纳米管的合成与生长机理

以非晶硼和氧化镍纳米颗粒为原料,在氨气中1100 oC下合成了毛刺状竹节结构的氮化硼纳米管. 利用X射线衍射和透射电镜研究了氮化硼纳米管的结构和形貌. 竹节结构纳米管表面的毛刺是六方氮化硼的纳米薄片. 提出了一种基于固态硼和气态二氧化硼扩散的毛刺形貌生长机理.     

压力对GdoBr:Eu晶场参数的影响

 在室温下测量了GdoBr:Eu的常压和高压荧光谱，光谱范围在13 000~21 500 cm^-1之间，压力至12 GPa。由光谱数据得到了Eu³⁺晶场能级随压力的变化曲线。⁷F_0～5能级随压力的变化规律比较复杂，而⁵D_0~2各能均随压力的升高几乎线性地降低。在基态谱项⁷F的49个状态上进行了晶场拟合计算，所得常压下的5个非零晶场参数分别为：B₀²＝-1 124.0 cm^-1，B₀⁴＝-969.6 cm^-1，B₄⁴＝827.9 cm^-1，B₀⁶＝889.6 cm^-1，B₄⁶＝377.0 cm^-1。高压下的计算结果表明，B₀⁴、B₀⁶这两个晶场参数随压力的增加而增大，B₄⁶随压力的增加而减小，而B₀²、B₄⁴随压力的变化有些起伏。晶场强度在8 GPa以下随压力增加而减小，其后开始变强。     

First-Principles Studies on Properties of Boron-Related Impurities in c-BN

We investigate, by first-principles calculations, the pressure dependence of formation enthalpies and defective geometry and bulk modulus of boron-related impurities （VB, Cs, NB, and OB） with different charged states in cubic boron nitride （c-BN） using a supercell approach. It is found that the nitrogen atoms surrounding the defect relax inward in the case of CB, while the nitrogen atoms relax outward in the other cases. These boron-related impurities become much more stable and have larger concentration with increasing pressure. The impurity CB^＋1 is found to have the lowest formation enthalpy, make the material exhibit semiconductor characters and have the bulk modulus higher than ideal c-BN and than those in the cases of other impurities. Our results suggest that the hardness of c-BN may be strengthened when a carbon atom substitutes at a B site.     

Hydrogen storage in boron nitride and carbon clusters studied by molecular orbital calculations

Possibility of hydrogen gas storage in carbon (C) and boron nitride (BN) clusters was investigated by molecular orbital calculations. Chemisorption calculation was carried out for C₆₀, B₂₄N₂₄ and B₃₆N₃₆ with changing position of hydrogen atom to compare the bonding energy at carbon, nitrogen and boron, tetragonal and hexagonal rings. Chemisorption calculation of hydrogen for BN clusters showed that hydrogen bondings with nitrogen atoms and tetragonal rings were the most stable. Stability of H₂ molecules inside BN and C clusters was also investigated by molecular orbital calculations. C and BN clusters showed possibility of hydrogen storage of 6.5 and 4.9 wt%, respectively.     

Amantadine antiparkinsonian drug adsorption on the AlN and BN nanoclusters: A computational study

To find a sensor for Amantadine (AM) antiparkinsonian drug, we studied its interaction with Al₁₂N₁₂ and B₁₂N₁₂ nanoclusters by density functional theory calculations. The AM molecule attaches via its –NH₂ group to the Al or B atoms of Al₁₂N₁₂ or B₁₂N₁₂ with Gibbs free energy change about −31.5 or −26.1 kcal/mol. Increasing the AM concentration, the interaction becomes weaker due to steric effects. The AM adsorbs on the Al₁₂N₁₂ and B₁₂N₁₂ with two different mechanisms, including electrostatic and charge transfer, respectively. The AM significantly reduces the Al₁₂N₁₂ work function from 4.50 to 3.66 eV, increasing the electron field emission. Thus, the AlN cluster may be a work function type sensor. Upon the AM adsorption on the BN cage, the HOMO level is largely destabilized, reducing the E_g from 6.84 to 5.01 eV which largely increases the electrical conductivity. This indicates that the BN cluster may be a potential electronic sensor.     

BaCuO2.5在高压下的状态方程与电学性质

 在活塞-圆筒式高压装置上研究了BaCuO_2.5在4.5 GPa内的p-V关系,给出了其状态方程、Grüneisen参数γ₀、零压体弹模量B₀以及B₀的压力导数B′₀。并在金刚石压砧装置（DAC）上测量了样品的电阻、电容随压力变化的关系,结果表明在0~20 GPa内没有发生相变。     

Formation Mechanisms of Electrical Conductivity and Optical Properties of ZnO:N Film Produced by Annealing Treatment

The effects of annealing on the chemical states of N dopant, electrical, and optical properties of N-doped ZnO film grown by molecular beam epitaxy (MBE) are investigated. Both the as-grown ZnO:N film and the film annealed in N₂ are of n-type conductivity, whereas the conductivity converts into p-type conductivity for the film annealed in O₂. We suggest that the transformation of conductivity is ascribed to the change in ratio of the N molecular number on O site (N₂)_O to the N atom number on O site (N_O) in ZnO:N films under the various annealed atmosphere. For the ZnO:N film annealed in N₂, the percentage content of (N₂)_O is larger than that of N_O, i.e.the ratio >1, resulting in the n-type conductivity. However, in the case of the ZnO:N film annealed in O₂, the percentage content of (N₂)_O is fewer than that of N_O, i.e., the ratio <1, giving rise to the p-type conductivity. There is an obvious difference between low-temperature (80K) PL spectra of ZnO:N film annealed in N₂ and that of ZnO:N film annealed in O₂. An emission band located at 3.358eV is observed in the spectra of the ZnO:N film after annealed in N₂, this emission band is due to donor-bound exciton (D⁰X). After annealed in O₂, the PL of the donor-bound exciton disappeared, an emission band located at 3.348eV is observed, this emission band is assigned to acceptor-bound exciton (A⁰X).     

Thorn-like BN nanostructures

Thorn-like BN nanostructures that the nanosize hexagonal BN (h-BN) layers are randomly stacked looking like thorns were synthesized using thermal chemical vapor deposition of B/B₂O₃ under the flow of NH₃ at 1200 °C. They can grow self-assembled forming the microsize lumps, and also deposit as sheathing layers on the pre-grown SiC nanowires with a controlled thickness in the range 20-100 nm. The spreading of the thorn-like BN layers as the sheathing layers results in a significantly enhanced surface area, 2400 m²/g.     

Photoluminescence Study of He ions hot-implanted Sapphire After 208Pb27+ of 230MeV Irradiation

In the present work the photoluminescence (PL)character of sapphire implanted with He ions and subsequently irradiated with ²⁰⁸Pb²⁷⁺ of 1.1MeV/u was studied. Sapphire single crystals were implanted with 110keV He ions at 600K temperature to fluences ranging from (0.5 to 2)×10¹⁷ ions/cm², some of them were subsequently irradiated with ²⁰⁸ Pb²⁷⁺.From experimental results we found PL spectra peaks at 375nm, 413nm, and 450nm, and it's intensity gets maximum at fluence of 5×10¹⁶ He ions/cm². Also we found a new peak at 390nm after subsequent ²⁰⁸ Pb²⁷⁺ irradiation, which is possibly due to the crystallized sediment containing nano crystal Al₂O₃ appeared on the sample surface.     

非晶铁基合金中两类不同的压磁效应

 本文详细介绍了在0.000 1~2.3 GPa流体静压力下测量三种非晶合金饱和磁感应强度B_s和最大磁导率μ_max的实验方法。实验结果表明：三种非晶合金受压后B_s和μ_max表现各异，可归为两大类。（1）第一类压磁效应：总趋势是B_s和μ_max都随压力增加而下降，但在几个压力区B_s反常增高。如Fe₇₅Ni₅Si₅B₁₅非晶合金B_s随压力增加均匀下降，(Fe_0.85Co_0.15)Cu_0.4Si_4.4B_13.2非晶合金的B_s随压力增加降—升—再降。（2）第二类压磁效应，如Fe_78.75Cu_1.25Si₅B₁₅非晶合金的B_s和μ_max随压力增加都有未见报导过的微弱升高。分别结合局域电子模型的交换作用理论和巡游电子模型的刚带理论进行了讨论。     

Geometric and electronic structures of B12C6N6 fullerene

An electron deficient fullerene B₁₂C₆N₆ is studied by using ab initio calculations. The structure is generated by replacing N with C in the B₁₂N₁₂ cage to ensure only B–C and B–N bonds are formed. All the possible isomers are optimized and the low energy structures are determined. C and N atoms in the low energy isomers are inclined to segregate and form B₂C₂ and B₂N₂ squares. Natural bond analysis shows that the atomic orbitals of B, C and N in this cage hybrid approximately in sp^2.3 and then form B–C and B–N bonds. The 2p orbitals perpendicular to the cage surface are partially occupied and the molecular orbitals formed by these orbitals are highly delocalized. The natural charge on N is about −1.17 in both B₁₂N₁₂ and B₁₂C₆N₆, and the charge on C is −0.72 to −0.60. The molecular orbital compositions show that the B–N bonds are the same in B₁₂N₁₂ and B₁₂C₆N₆, and the B–C bonds possess stronger covalent character. The HOMO of B₁₂C₆N₆ is formed by 2p of B and C, and the LUMO is formed by 2p of C. The energy gap of C₂₄, B₁₂N₁₂ and B₁₂C₆N₆ is 2.52, 6.84 and 3.22 eV, respectively.     

Structural,magneto and optical properties of BX − 1NXC and BXNX − 1C cages (X = 12, 24 and 36)

The effect of carbon doping on the structural, optical and magneto properties of the B_XN_X cages has been studied using the B3LYP/6-31G^* level of density functional theory. With replacing one B or N atom with one C atom on the B_XN_X cages, the structural and symmetric properties, the optical absorption spectra and the band gaps of the B_XN_X cages change and the B_XN_X cages become magnetic. Our calculations conclude that the B_{X ? 1}N_XC and B_XN_{X ? 1}C cages can be interesting candidates for application in optoelectronics and spintronics.     

Properties of a New Nonlinear Optical Crystal CdZn2B2O6

Cadmium dizinc diborate （CdZn2B2O6） single crystals have been grown for the first time. The crystal structure of CdZn2B2O6 is the same as that of the Cd3Zn3B4O12. The x-ray diffraction, infrared and Raman spectra, differential scanning calorimetry analysis and density indicate that the physical and chemical properties of both crystals are very similar. Especially, the nonlinear optical coefficients of CdZn2B2O6 and Cd3Zn3B4O12 crystals are 2.6 and 2.4 times as large as that of KH2PO4 crystal respectively. Chemical etching experiments indicated that these crystals are very stable in neutral solution and not hygroscopic in air at room temperature.     

片状h-CN化合物的高温高压化学合成与表征

 以高温烧结三聚氰胺制得的CNH化合物为C、N源，与分析纯单质硼粉以一定比例混合，在5.0～5.5 GPa、1 400~1 500 ℃高温高压条件下，经化学反应合成了六角硼碳氮（h-BCN）晶体。用傅立叶变换红外光谱（FTIR）和X射线光电子能谱（XPS）对产物进行了表征，结果表明，得到了含碳量较高的六方结构B_0.18C_0.66N_0.16化合物，成分接近于BC₄N，硼、碳、氮是以原子化合的形式存在；XRD分析确定该合成产物具有六角网状结构；SEM测量结果表明，B-C-N晶体具有片状六角形貌，尺寸在1 μm左右。     

Determination of J/ψ Leptonic Branching Fraction Via ψ(2S)→π+π－J/ψ

Two processes ψ(2S)→π⁺π^－J/ψ,J/ψ→1⁺1^－ and J/ψ→anything are carefully studied to get the J/ψ leptonic branching fractions with the ψ(2S)data at BES/BEPC.The results are B(J/ψ→e⁺e^－)=(5.90±0.07±0.16)% and B(J/ψ→μ⁺μ^－)=(5.96 ±0.08±0.16)%,and B_e/B_μ is estimated to be 0.990±0.018±0.024.Assuming B_e=B_μ,the leptonic branching fraction of the J/ψ is B(J/ψ→1⁺1^－)=(5.93±0.05 ± 0. 16 )%.This result is used to estimate the QCD scale factor ∧(nf/MS) and the strong coupling constant α_s.