推、拉电子基团对水杨醛缩胺分子电子结构和非线性光学性质的影响

采用量子化学半经验FF／PM3方法,讨论了水杨醛缩苯胺分子中两苯环的对位被推、拉电子基团取代后,体系电子结构和非线性光学性质的变化,考查了分子电子结构对非线性光学性质影响的微观本质,得到的具有给体－共轭桥键－受体型结构的水杨醛缩苯胺分子应显示良好的非线光学性质。     

新型低带隙聚合物结构和性质的理论研究

本文将3,4-次乙烯二氧噻吩（VDOT）与噻吩并[3,4-b]吡嗪（TP）,呋喃并[3,4-b]吡嗪（FP）和6H-吡咯并[3,4-b]吡嗪（PP）组合,获得了一系列3,4-次乙烯二氧噻吩衍生物.采用密度泛函理论（DFT）在B3LYP/6-31G＊理论水平下对其单体、低聚物和聚合物的结构和电子性质进行了深入的理论研究.通过分析键长的变化、中心键性质,Wiberg键级（WBI）以及核独立化学位移,发现随着聚合度的增加物质的共轭性也随之增加.为了了解不同的VDOT与TP、FP、PP比例对电子性质的影响,对V-P比例为1：1、1：2和2：1时的计算结果进行了对比分析,结果表明,V-P比例为1：2化合物共轭性最好,而2：1的共轭性最差.由于1：2的二聚物具有较大的电子迁移速率,其相应的聚合物可能是潜在的电子传输材料.同时,聚合物的能带结构显示V-P比例为1：1的聚合物（包括（VDOT-TP）n,（VDOT-FP）n和（VDOT-TP）n）具有相对低的带隙和很宽的带宽,可以做为潜在的导电材料.另外,（VDOT-BTP）n和（VDOT-BFP）n有着非常低的带隙（分别为0.73和0.87eV）,且拥有合适的带宽,也是良好的本征导电材料.     

Crystal and electronic band structure of IrTe2: Evidence of anionic bonds in a CdI2-like arrangement

The Rietveld structure determination of IrTe₂ showed that this phase differs from the CdI₂?like arrangement, with Te–Te multiple bonds (mean d_Te-Te = 3.528 Å) corresponding to Te^?1.5 anions, in agreement with the charge balance Ir³⁺(Te^?1.5)₂, the Iridium ion being d⁶ low spin. This new polymeric-CdI₂ structural type is shared by several other tellurides, namely: RhTe₂, CoTe_1.7, NiTe_1-x, PdTe₂, and PtTe₂, and its occurrence explains the abnormally low c/a ratio (1.38) of the hexagonal cell parameters. IrTe₂ band structure shows a strong degree of hybridization and mixing between the d cationic and p anionic levels. From the negative total overlap population between neighbour Ir³⁺ cations at the Fermi level, it can be inferred that the metallic conductivity of the phase involves the Tellurium anions through their 3D network. The crystal orbital overlap population curves for the Te–Te bonds indicate that electrons donated to the compound should fill anti-bonding levels, allowing for a breaking of these links, and possibly restoring a classical anionic stacking.     

First principles study on the structure and electronic properties of 2‐nitrimino‐1‐nitroimidazolidine

The properties of 2‐Nitrimino‐1‐nitroimidazolidine are calculated by using SIESTA code, which adopts the standard Kohn‐Sham self‐consistent density functional method in the local density approximation. The structures and electronic properties are analyzed, and the factors that affect the impact sensitivity are discussed based on the crystal structure, band energy, and projected density of state. The reason for the smaller impact sensitivity compared to RDX (hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine) is also explored from several respects such as the weakest bond dissociation energy in single molecule, and hydrogen bond, band gap in the crystal. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

The effect of covalent contact between solvent molecules and the VO(DMSO) 5 2+ ion on the electronic structure of the ion

The dissolution of the vanadyl complex VO(DMSO)₅(CLO₄)₂ in alcohols ROH (R= Me, Et, or Prⁿ) results in the appearance of a new absorption band at 372 nm in the electronic absorption spectra of the vanadyl ion. The calculation of the OVO₅ ²⁺ ion by the X-scattering wave method is carried out to interpret the spectra. It is shown that the new band in the spectrum of the VO(DMSO)₄OHR²⁺ complex corresponds to the b₂a₁ transition in the OVO₅ ²⁺ ion. However, this transition is not a pure d-d transition due to strong covalent bonding and a significant contribution from the AO 2p of oxygen to the a₁ MO. The appearance of the new absorption band in the electronic spectra of the vanadyl complexes is caused by the participation of ligand orbitals in bond formation.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 699–702, April, 1995.     

河豚毒素(TTX)及其衍生物的电子结构和构效关系及与石房蛤毒素(STX)的比较研究

对河豚毒素(TTX)及其五个衍生物进行了量子化学计算, 根据对其电子结构及相关分析研究结果, 结合其空间结构特点, 讨论了它们的活性部位、作用方式及构效关系, 发现胍基是最重要的正电中心,在与受体作用时发挥接受电子的重要作用; O(17), O(18), O(15),O(21), O(19)等氧原子是供电子的主要负电部位。对TTX与石房蛤毒素(STX)进行了电子结构和空间结构比较, 发现它们具有相似的电子结构特征, 而且主要活性部位在空间位置上基本相互对应。这表明钠离子通道阻断剂在与受体相互作用时具有共同的结构特征和作用方式, 同时也为探讨受体结构提供了有价值的信息。     

Complex investigation of multilayer nanostructure of a‐Si/SiO1.9 by probe and spectroscopic analysis techniques. Visualization of the band structure. Studying of the band structure of the suboxide border layers

This article describes an integrated approach to the study of multilayer nanostructures of a‐Si/SiO_1.9 as a potential model to study the influence of the effects arising at the interface of Si/SiO₂ under the influence of ionizing radiation. The results of the functional layers of amorphous silicon and silicon dioxide surface topology investigation have been disclosed. The possibility of application of a band gap contrast in electron probe studies by means of electron energy filtering during the detection process has been demonstrated. Changes in valence band and band gap through depth of the a‐Si/SiO_1.9 nanostructure have been registered. As part of the study, density of states of the a‐Si/SiO_1.9 multilayer nanostructures and depth distribution of surface suboxide layers of native oxide of amorphous silicon have been reconstructed using the determination of an effective mean free path of the electrons by the TPP2M algorithm in conjunction with PARXPS and REELS measurements. Copyright © 2015 John Wiley & Sons, Ltd.     

On the electronic band structure of periodic β-pleated sheet polypeptides in the presence of water and ions

The structure of the possible water surroundings of several periodic polypeptides in the -pleated sheet conformation has been determined by Monte-Carlo calculations. The resulting water positions have been used to calculate the band structure of the polymers in the effective field of these water molecules. In addition, similar calculations have been performed with sodium ions in the solution. It has been found that the changes of the band widths and of the band gaps are less than 1.8 eV in the presence of water and less than 1.1 eV in the presence of water and ions. The band positions themselves are, however, shifted by up to 3.7 eV in the presence of water and by up to 6 eV in the presence of water and ions.Dedicated to Professor J. Koutecký on the occasion of his 65th birthday     

PEO／V2O5复合薄膜中Li^＋的位置与电子结构研究

采用自洽场离散变分Xα（SCC-DV-Xα）方法对纯V2O5及夹层V2O5的能带结构、态密度、键强度、电子集居数等进行了研究，结果表明，Li^ 引入V2O5层间的最佳位置在在双键氧之下（或之上），且靠近层的中心位置，此时它与周围原子间的作用力非常微弱，并且材料的导电性增强，使夹层复合材料Li^ 注入／脱出具有很好的可逆性和较好的光学性质。     

Characterization and optical properties of mechanochemically synthesized molybdenum-doped rutile nanoparticles and their electronic structure studies by density functional theory

The optical and electronic properties of molybdenum (Mo) doped rutile TiO₂ prepared by the mechanochemical method were studied both experimentally and using density functional theory (DFT). The synthesized nanoparticles were characterized by XRD, TEM, EDS-MAP, and XPS. The XRD results showed the successful incorporation of Mo in the rutile crystal lattice. High-resolution TEM images illustrated a decreasing trend in the (110) d-spacing for samples doped up to 3 at%. The shift toward higher binding energies in the XPS spectra was due to the higher oxidization tendencies of Mo⁵⁺ and Mo⁶⁺ substituted in Ti⁴⁺ sites. The optical behavior of samples was examined by UV–Vis and photoluminescence spectroscopy. The bandgap energy value of rutile was reduced from 3.0 eV to 2.4 eV by 2 at% Mo doping. The DFT calculations showed a reduction of bandgap energy value of rutile to 2.35 eV with 2 at% Mo, which is in harmony with the experimental results. The creation of energy states below the conduction band because of Mo doping was identified as the reason for reducing the bandgap energy and photoluminescence emission of rutile.     

Nitrogen depth distribution, interface and structure analysis of SiNx layers produced by low-energy ion implantation

Thin silicon nitride (SiN _x ) layers with the stoichiometric N/Si ratio of 1.33 in the maximum of the concentration depth distributions of nitrogen were produced by implanting 10 keV¹⁵N ₂ ⁺ in 100 silicon at room temperature under high vacuum conditions. The depth distribution of the implanted isotope was measured by resonance nuclear reaction analysis (NRA), whereas the layer structure of the implanted region and the geometrical thickness of the layers were characterised by high resolution transmission electron microscopy (TEM). SiN _x layers with a thickness of about 30 nm were determined by NRA. Channeling Rutherford backscattering spectrometry was used to determine the disorder in the silicon substrate. Sharp interfaces of a few nanometers between the highly disordered implanted region and the crystalline structure of the substrate thickness were observed by TEM. The high thermal stability of SiN _x layers with N/Si ratios from under to over stoichiometric could be shown by electron beam rapid thermal annealing (1100 °C for 15 s, ramping up and down 5 °C/s) and NRA.     

Determining the intermolecular structure in the S0 and S1 states of the phenol dimer by rotationally resolved electronic spectroscopy.

The rotationally resolved UV spectra of the electronic origins of five isotopomers of the phenol dimer have been measured. The complex spectra are analyzed using a fitting strategy based on a genetic algorithm. The intermolecular geometry parameters have been determined from the inertial parameters for both electronic states and compared to the results of ab initio calculations. In the electronic ground state, a larger hydrogen-bond length than in the ab initio calculations is found together with a smaller tilt angle of the aromatic rings, which shows a more pronounced dispersion interaction. In the electronically excited state, the hydrogen-bond length decreases, as has been found for other hydrogen-bonded clusters of phenol, and the two aromatic rings are tilted less toward each other.     

The investigation of NbO2 and Nb2O5 electronic structure by XPS,UPS and first principles methods

In this paper, the electronic structures of NbO₂ and Nb₂O₅ are theoretically and experimentally analyzed. The oxides in the samples are mainly consisted of NbO₂ and NbO, whereas the outmost layer of the samples is NbO₂. After exposure to air, the outermost layer on all niobium samples is Nb₂O₅. The photoelectrons from the first 2–4 Å contribute to the spectra, so the valence band structure of NbO₂ and Nb₂O₅ can be confirmed from ultraviolet photoelectron spectroscopy (UPS). By comparing the UPS with density of state results, the electronic structure of NbO₂ and Nb₂O₅ can be distinguished from each other, and then the electronic structure was deconvoluted into several electronic states. The agreement between experimental result and theory is, in the best case, satisfactory. Copyright © 2013 John Wiley & Sons, Ltd.     

Local structure and oxidation state of uranium in some ternary oxides: X-ray absorption analysis

We investigated the local atomic and electronic structures of two related systematic sets of ternary uranium oxides, NaUO₃-KUO₃-RbUO₃ and BaUO₃-Ba₂U₂O₇-BaUO₄, by measuring the X-ray absorption near edge structure (XANES). The results are compared with calculations based on a self-consistent real space full multiple scattering analysis. We found a very good agreement between measured and calculated spectra, which indicates that the uranium ions are in a pure U⁵⁺ oxidation state in these compounds. The low energy shoulder observed in the U L₃ edge XANES is an intrinsic feature of the uranium unoccupied 6d electronic states of the U⁵⁺ ions within the studied materials. Specific double shoulder features in the higher energy range of the U L₃ edge XANES can be interpreted as indicative of the pure cubic perovskite structure.     

Chemical profile and difference analysis of four parts of Strobilanthes sarcorrhiza by ultrafast flow liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry and multivariate statistical analysis

Strobilanthes sarcorrhiza (CTS) is a medicinal plant with various pharmacological effects such as tonifying kidney and anti-inflammatory. However, the chemical composition and difference of its four parts (leaves, stems, rhizomes, and root tubers) have been rarely reported. In this study, ultrafast flow liquid chromatography coupled with quadrupole-time-of-flight MS was applied to analyze the chemical profile of CTS and identify 55 compounds, including terpenoids, phenylethanol glycosides, fatty acid derivatives, chain glycosides, flavonoid glycosides, and others. Among these compounds, 34 compounds were first identified in CTS. They were mainly terpenoids, phenylethanol glycosides, fatty acid derivatives, and so forth. Multivariate statistical analysis, such as principal component analysis and orthogonal partial least squares-discriminant analysis were also used to evaluate the difference in chemical compounds from the four parts of CTS. The results showed that phenylethanol glycosides were the main compounds of the underground parts, while terpenoids were the main compounds of the aboveground parts. This study revealed the chemical diversity and similarity of CTS and suggested that the rhizomes could be used as an alternative medicinal part to improve the resource utilization of CTS.     

Crystal structure,optical properties,and theory study of a 1-D bromoplumbate stabilized by in situ generated N-alkylated DABCO cation

We report the exploration of the stabilization effect of the in situ generated N-alkylated DABCO (DABCO = 1,4-diazabicyclo[2.2.2]octane) cation in the family of bromoplumbates and a 1-D bromoplumbate, (Et₂DABCO)_2n(Pb₃Br₁₀)_n (1), has been prepared by solvothermal conditions. Optical diffuse reflectance determination shows the band gap of 1 is 3.69 eV, which manifests that 1 is a wide band gap semiconductor. Compared with the band gap of bulk PbBr₂ (3.84 eV), 1 exhibits 0.15 eV red shift of absorption edge. While for the reported iodo analogs of this compound, (MPDA)_2n(Pb₃I₁₀)_n and (Et₂DABCO)_2n(Pb₃I₁₀)_n, they exhibit 0.53 and 0.47 eV blue shift of the energy gaps compared with the measured value of 2.30 eV for bulk PbI₂, respectively. The photoluminescent study of 1 shows that it exhibits a broad emission band centered at 697 nm upon photoexcitation by 345 nm (amount to 3.59 eV). The calculated density of states manifests the theoretical value of the band gap of 1 is 3.422 eV and the origination of photoluminescence can be ascribed to the transition of bonding electrons of Br^– anion to the empty orbits of Pb(II) ion.     

(111)应变对正交相Ca_2P_(0.25)Si_(0.75)能带结构及光学性质影响的理论研究

采用第一性原理平面波贋势方法对(111)应变下正交相Ca2P0.25Si0.75的能带结构及光学性质进行模拟计算.计算结果表明:(111)面在晶格发生100%~104%张应变时,带隙随着应变增加而增大;在晶格发生104%~112%压应变时,带隙随着张应变的增加而减小;88%~100%压应变时,带隙随着压应变的增加而减小;当压应变达到88%后转变为导体.当施加应变后光学性质发生显著的变化,随着压应变的增加静态介电常数、折射率逐渐减小,张应变则反之.施加压应变反射向高能方向偏移,施加张应变反射向低能方向偏移.施压应变吸收谱增大,施加张应变吸收谱变小.综上所述,应变可以改变Ca2P0.25Si0.75的电子结构和光学常数,是调节Ca2P0.25Si0.75光电传输性能的有效手段.     

Analysis of flame retardant additives in polymer fractions of waste of electric and electronic equipment (WEEE) by means of HPLC-UV/MS and GPC-HPLC-UV

An HPLC-UV/MS method has been developed to identify and quantify flame retardants in post-consumer plastics from waste of electric and electronic equipment (WEEE). Atmospheric pressure chemical ionisation spectra of 15 brominated and phosphate-based flame retardants were recorded and interpreted. The method was applied to detect flame retardant additives in polymer extracts obtained from pressurised liquid extraction of solid polymers. In addition, a screening method was developed for soluble styrene polymers to isolate a flame retardant fraction through the application of gel permeation chromatography (GPC). This fraction was transferred to an online-coupled HPLC column and detected by UV spectroscopy, which allowed a reliable qualitative and quantitative analysis of brominated flame retardants in the polymer solutions.     

Change in a protein's electronic structure induced by an explicit solvent: an ab initio fragment molecular orbital study of ubiquitin

The effect of solvation on the electronic structure of the ubiquitin protein was analyzed using the ab initio fragment molecular orbital (FMO) method. FMO calculations were performed for the protein in vacuo, and the protein was immersed in an explicit solvent shell as thick as 12 A at the HF or MP2 level by using the 6-31G* basis set. The protein's physical properties examined were the net charge, the dipole moment, the internal energy, and the solvent interaction energy. Comparison of the computational results revealed the following changes in the protein upon solvation. First, the positively charged amino acid residues on the protein surface drew electrons from the solvent, while the negatively charged ones transfer electrons to the solvent. Second, the dipole moment of the protein was enhanced as a result of the polarization. Third, the internal energy of the protein was destabilized, but the destabilization was more than compensated for by the generation of a favorable protein-solvent interaction. Finally, the energetic changes were elicited both by the electron correlation effect of the first solvent shell and by the electrostatic effect of more distant solvent molecules. These findings were consistent with the picture of the solvated protein being a polarizable molecule dissolved in a dielectric media.