Structural, electronic, and magnetic properties of boron cluster anions doped with aluminum: BnAl- (2≤n≤9)

The geometrical structures, relative stabilities, electronic and magnetic properties of small B n Al (2 ≤ n ≤ 9) clusters are systematically investigated by using the first-principles density functional theory. The results show that the Al atom prefers to reside either on the outer-side or above the surface, but not in the centre of the clusters in all of the most stable B n Al (2 ≤ n ≤ 9) isomers and the one excess electron is strong enough to modify the geometries of some specific sizes of the neutral clusters. All the results of the analysis for the fragmentation energies, the second-order difference of energies, and the highest occupied-lowest unoccupied molecular orbital energy gaps show that B 4 Al and B 8 Al clusters each have a higher relative stability. Especially, the B 8 Al cluster has the most enhanced chemical stability. Furthermore, both the local magnetic moments and the total magnetic moments display a pronounced odd-even oscillation with the number of boron atoms, and the magnetic effects arise mainly from the boron atoms except for the B 7 Al and B 9 Al clusters.     

基于梯度一致性约束的多光谱/全色影像最大后验融合方法

多光谱/全色影像融合可以得到高空间分辨率的多光谱影像,在影像解译和分类等方面具有十分重要的意义。提出一种基于梯度一致性约束的遥感影像融合方法。该方法在最大后验概率框架下,通过梯度一致性约束建立理想高空间分辨率多光谱影像和全色影像之间的关系,并结合多光谱影像观测模型和HuberMarkov影像先验,构建融合目标函数,最后采用梯度下降法求解得到融合影像。本文方法在目标函数中引入了梯度一致性约束,克服了现有的同类方法受限于波段数量的缺陷,同时在求解中自适应确定每个波段的迭代步长,充分顾及了各波段的光谱特性,从而既确保了融合影像的光谱信息保真度,也提高了融合影像的空间信息融入度。通过IKONOS和WorldView-2影像对该方法进行了验证,并和GS,AIHS和AMBF等融合方法从定性和定量两方面进行了比较分析。实验结果表明,相比于其他方法,该方法可以在更好保持光谱信息的同时增强影像的空间分辨率,具有更广泛的适用范围和更佳的融合效果。     

九配位(NH4)3[Dy(TTHA)]·5H2O配合物的合成及结构测定

报道了新型配合物(NH4)3[Dy(TTHA)]*5H2O(TTHA=三乙四胺六乙酸)的分子结构和晶体结构. 配合物晶体参数为 单斜晶系, P2(1)/c空间群, a=1.0353(3) nm, b=1.2746(4) nm, c=2.3141(7) nm, β=91.005(5)°, V=3.053(15 nm3), Z=4, M=795.10, Dc=1.730 g*cm-3, μ= 2.532 mm-1, F(000)=1620. 其R和Rw值分别为0.0332和0.0924(对5390个独立的衍射点), R和Rw值分别为0.0460和0.1012(对所有12395个衍射点). 配合物(NH4)3[Dy(TTHA)]*5H2O中的[Dy(TTHA)]3- 部分是一个九配位的非标准单帽四方反棱柱体结构. 十齿TTHA配体提供四个胺基氮原子和五个羧基氧原子与中心金属Dy(Ⅲ)离子配位. 为使[Dy(TTHA)]3-部分在体内具定向功能, 结构中未参与配位的自由羧酸基(-CH2COO-)可采用某些生物分子修饰.     

Molecular beam epitaxy growth of monolayer hexagonal MnTe2 on Si(111) substrate

Monolayer MnTe₂ stabilized as 1T structure has been theoretically predicted to be a two-dimensional (2D) ferromagnetic metal and can be tuned via strain engineering. There is no naturally van der Waals (vdW) layered MnTe₂ bulk, leaving mechanical exfoliation impossible to prepare monolayer MnTe₂. Herein, by means of molecular beam epitaxy (MBE), we successfully prepared monolayer hexagonal MnTe₂ on Si(111) under Te rich condition. Sharp reflection high-energy electron diffraction (RHEED) and low-energy electron diffraction (LEED) patterns suggest the monolayer is atomically flat without surface reconstruction. The valence state of Mn⁴⁺ and the atom ratio of ([Te]:[Mn]) further confirm the MnTe₂ compound. Scanning tunneling spectroscopy (STS) shows the hexagonal MnTe₂ monolayer is a semiconductor with a large bandgap of ~2.78 eV. The valence-band maximum (VBM) locates at the Γ point, as illustrated by angle-resolved photoemission spectroscopy (ARPES), below which three hole-type bands with parabolic dispersion can be identified. The successful synthesis of monolayer MnTe₂ film provides a new platform to investigate the 2D magnetism.     

共价有机框架COF66/COF366的电子结构:从单体到二维平面聚合物

二维共价有机骨架(COFs)是由有机小分子结构单元通过共价键连接形成的一类新型的、具有周期性多孔网络框架结构的结晶性聚合物,在未来的光电功能材料领域有着优异的应用前景.因此,研究COFs结构与性质之间的内在关系,并以此反馈分子设计,将对此类光电功能材料的发展有着至关重要的意义.以共价有机框架66(COF66)和共价有机框架366(COF366)为例,分析了有机构建单元、COFs片段分子和周期性二维平面聚合物前线轨道能级/分布以及电子性质,阐述了有机构建单元与COFs电子结构之间的内在关系.计算结果表明,有机构建单元小分子的几何构型会影响其二维周期性平面聚合物的结构.另外,有机构建单元自身的前线轨道能级的相对位置会直接影响到COFs片段分子前线轨道的能级和分布,也决定了片段分子的电离势和电子亲和能.COFs周期性结构的电子性质与片段分子相似.因此,有机构建单元的前线轨道能级以及匹配情况决定了COFs周期性结构的电子性质.除此之外,中心分子和连接分子之间的共轭相互作用越大,电子耦合作用也相应较大,价带顶和导带底则会相对比较分散,会更有助于载流子在二维平面结构内的迁移.     

锂离子电池电解液中六氟磷酸锂浓度的离子色谱测定法

用离子色谱法测试锂离子电池电解液中的电解质(LiPF6)浓度,通过一系列条件实验确定了最佳前处理方式:选择逆王水作为分解处理剂;其用量与电解液等体积;作用时间在12 h以上,结果表明,F-和PO43-的回收率均达到100%以上,且根据PO3-计算得到的LiPF浓度相对误差为1.2%,具有较高的定量准确度。     

九配位K_3[Ho(nta)_2(H_2O)]·5H_2O和八配位NH_4[Ho(cdta)(H_2O)_2]·4.5H_2O配合物的合成及结构

报道了稀土金属Ho~(III)离子氨基多羧酸（nta=氨基三乙酸，cdta=反式-1， 2-环乙二氨四乙酸）配合物的合成及分子结构和晶体结构的测定。具体结果如下： （a)分子式K_3[Ho(nta)_2(H_2O)]·5H_2O，单斜晶系，C2/c空间群，a = 1.5364 (8) nm, b = 1.2881(7) nm，c = 2.6163(13) nm, β = 96.140(9)°, V = 5. 416(5) nm~3，Z = 8，D_c = 1.932 g/cm~3, μ = 3.635 nm~(-1)和F(000) = 2944。其R和R_w值分别为0.0310和0.0675(对4509个独立的衍射点），R和R_w值分 别为0.0442和0.0707（对所有10336个衍射点）。K_3[Ho(nta)_2(H_2O)]·5H_2O配 合物中，Ho~(III)N_2O_7部分是一个九配位单帽四方反棱柱体结构。(b)分子式 NH_4[Ho(cdta)(H_2O)_2]·4.5H_2O，三斜晶系，P1，空间群，a = 0.8636(3) nm, b = 1.0072(3) nm, c = 1.4457(5) nm, α = 88.382(5)°, β = 75.275(5)°, γ = 88.382(5)°, V = 1.2154(7) nm~3, Z = 2, D_c = 1.657 g/cm~3, μ = 3.315 nm~(-1)和F(000) = 606。其R和R_w值分别为0.0283和0.0708（对4203个独 立的衍射点），R和R_w值分别为0.0325和0.0730(对所有4595个衍射点）。NH_4 [Ho(cdta)(H_2O)_2]·4.5H_2O配合物中Ho~(III)N_2O_6部分是一个八配位四方反 棱柱体结构。     

Structural,electronic, and magnetic properties of boron cluster anions doped with aluminum：BnAl-（2〈n〈9）

The geometrical structures, relative stabilities, electronic and magnetic properties of small BnAl-（2〈n〈9）clusters are systematicalyy investigated by using the first-principles density functional theory. The results show that the A1 atom prefers to reside either on the outer-side or above the surface, but not in the centre of the clusters in all of the most stable BnAl-（2〈n〈9） isomers and the one excess electron is strong enough to modify the geometries of some specific sizes of the neutral clusters. All the results of the analysis for the fragmentation energies, the second-order difference of energies, and the highest occupied-lowest unoccupied molecular orbital energy gaps show that B4A1- and B8A1- clusters each have a higher relative stability. Especially, the BsA1-cluster has the most enhanced chemical stability. Furthermore, both the local magnetic moments and the total magnetic moments display a pronounced oddeven oscillation with the number of boron atoms, and the magnetic effects arise mainly from the boron atoms except for the B7A1- and BgA1- clusters.     

外加电场对激光诱导Al等离子体发射光谱的影响

在低压环境下,由Nd:YAG脉冲激光器产生的1.06 μm激光烧蚀金属Al靶产生等离子体,观测了外加电场下其空间分辨发射光谱,并由此分析了谱线相对强度、谱线展宽随外加电压的演化特性.结果发现:原子谱线强度及其半高全宽随外加电压的增加均有明显增大,而离子谱线受外加电压的影响较小.从微观机制上分析推断:外加电场使非稳态等离子体中的电子作定向运动,加剧电子与原子之间的碰撞是上述结果的主要原因.此外,由发射光谱线的Stark展宽计算了等离子体电子密度,并由实验结果讨论电子密度随外加电压的演化特性和空间演化特性.     

Theoretical study on 2s2p^6np Rydberg states of Cu^19＋ ion

We report on the calculations of transition wavelengths and weighted oscillator strengths for 2s 2 2p 6-2s2p 6 np （4≤n≤20） electric dipole （E1） transitions of Cu 19+ ion.The flexible atomic code （FAC） has been adopted for the calculations.Comparisons are made with the experimental data available,showing that the present results for 4 ≤n≤6 are more accurate than the previous calculated values.Furthermore,combining the quantum defect theory （QDT） with the transition energies of 2s22p～6-2s2p～6np,the quantum defects for 2s2p 6 np Rydberg series of Cu～（19+）ion are determined.In addition,the energies of any highly excited states （n>20） for this series can be reliably predicted using the QDT and the given quantum defects.The ionization energies for Cu¹⁹⁺ and Cu²⁰⁺ ions are also calculated and they excellently accord with previous experimental and calculated values.