Theoretical Analysis on Geometry Structure and Electronic Structure of LaNi_4Co

The theoretical calculation of LaNi4Co, in which Co substituted for Ni at various sites, was performed by adopting the method of total energy based on the Density Functional Theory. The augmented plane wave function was selected as a basis set in combination with Ultra-soft Pseudopotential technology. The geometry of LaNi5 was optimized and the parameters and properties of the structure were given. The theoretical results accord well with experiments. This method provides a theoretical approach for the structure prediction of such alloy. The calculations of total energy, electronic density of states and Mulliken population of LaNi4Co were carried out. The electronic structure of LaNi4Co and the change of the electronic structure due to the Co-substitution in LaNi5 alloy were analyzed from the calculated results. The stability of the alloy in which Ni was partially substituted by Co at various sites was compared and the factors controlling stability were discussed. The theoretical value of formation heat was calculated.

Inverse Halogen Bonds Interactions Involving Br Atom in the Electronic Deficiency Systems of CH3＋… Br-Y （Y--H, CCH, CN, NC）

Inverse halogen bonds interactions involving Br in the electronic deficiency systems of CH3＋...Br-Y （Y=H, CCH, CN, NC） have been investigated by B3LYP/6- 311＋＋G（d, p） and MP2/6-311＋＋G（d, p） methods. The calculated interaction energies with basis set super-position error correction of the four IXBs complexes are 218.87, 219.48, 159.18, and 143.05kJ/mol （MP2/6-311＋＋G（d, p））, respectively. The relative stabilities of the four complexes increased in the order： CH3＋ … BrCN〈CH3＋…- BrNC〈CH3＋… BrH≈CH3＋ …BrCCH. Natural bond orbital theory analysis and the chemical shifts calculation of the related atoms revealed that the charges flow from Br-Y to CH3e. Here, the Br of Br-Y acts as both a halogen bond donor and an electron donor. Therefore, compared with conventional halogen bonds, the IXBs complexes formed between Br-Y and CH3＋. Atoms-in-molecules theory has been used to investigate the topological properties of the critical points of the four IXBs structures which have more covalent content.

Fractal analysis of polyferric chloride-humic acid(PFC-HA) flocs in different topological spaces

The fractal dimensions in different topological spaces of polyferric chloride-humic acid （PFC-HA） flocs, formed in flocculating different kinds of humic acids （HA） water at different initial pH （9.0, 7.0, 5.0） and PFC dosages, were calculated by effective densitymaximum diameter, image analysis, and N2 absorption-desorption methods, respectively. The mass fractal dimensions （De） of PFC-HA floes were calculated by bi-logarithm relation of effective density with maximum diameter and Logan empirical equation. The Df value was more than 2.0 at initial pH of 7,0, which was 11% and 13% higher than those at pH 9.0 and 5.0, respecively, indicating the most compact flocs formed in flocculated HA water at initial pH of 7.0. The image analysis for those flocs indicates that after flocculating the HA water at initial pH greater than 7.0 with PFC flocculant, the fractal dimensions of D2 （logA vs. logdL） and D3 （logVsphere vs. logdL） of PFC-HA floes decreased with the increase of PFC dosages, and PFC-HA floes showed a gradually looser structure. At the optimum dosage of PFC, the D2 （logA vs. logdL） values of the flocs show 14%-43% difference with their corresponding Dr, and they even had different tendency with the change of initial pH values. However, the D2 values of the floes formed at three different initial pH in HA solution had a same tendency with the corresponding Df. Based on fractal Frenkel-Halsey-HiU （FHH） adsorption and desorption equations, the pore surface fractal dimensions （Ds） for dried powders of PFC-HA flocs formed in HA water with initial pH 9.0 and 7.0 were all close to 2.9421, and the Ds values of flocs formed at initial pH 5.0 were less than 2.3746. It indicated that the pore surface fractal dimensions of PFC-HA floes dried powder mainly show the irregularity from the mesopore-size distribution and marcopore-size distribution.

Topology optimization design of the main structure of 6-DOF manipulator based on the variable density method

In order to solve the problems of too large mass,too complex structure and poor flexibility of the 6 DOF manipulator,the topological optimization theory based on variable density method is applied to the 6-DOF manipulator,the topology optimization of the main structural components of the manipulator is carried out with the help of the finite element software ANSYS,and the optimized structure is simplified according to the density distribution of the units and the requirements of manufacturability.the results are compared and analysed by static mechanics.It shows that the whole mass of the 6-DOF manipulator is reduced by 47.23%without changing the original mechanical properties after topological optimization,and the optimized model can meet the requirements of manufacturability,the optimization effect is signifcant,which can be used as a reference for the structure optimization of the 6-DOF manipulator.

Perspective:Chemical Information Encoded in Electron Density

In this perspective,we review the chemical information encoded in electron density and other ingredients used in semilocal functionals.This information is usually looked at from the functional point of view:the exchange density or the enhancement factor are discussed in terms of the reduced density gradient.However,what parts of a molecule do these 3D functions represent? We look atthese quantities in real space,aiming to understand the electronic structure information they encode and provide an insight from the quantum chemical topology(QCT).Generalized gradient approximations(GGAs) provide information about the presence of chemical interactions,whereas meta-GGAs can differentiate between the different bonding types.By merging these two techniques,we show new insight into the failures of semilocal functionals owing to three main errors:fractional charges,fractional spins,and non-covalent interactions.We build on simple models.We also analyze the delocalization error in hydrogen chains,showing the ability of QCT to reveal the delocalization error introduced by semilocal functionals.Then,we show how the analysis of localization can help understand the fractional spin error in alkali atoms,and how it can be used to correct it.Finally,we show that the poor description of GGAs of isodesmic reactions in alkanes is due to 1,3-interactions.

Study on the Intramolecular Hydrogen Bonds of Dibenzofurans, Xanthones and Anthraquinones with One or Two Positions Substituted by Hydroxyls

The thermodynamic properties of dibenzofurans （DFs）, xanthones （XTs） and an-thraquinones （AQs） with one and two positions substituted with hydroxyls in the ideal gas state at 298.15 K and 1.013×10^5 pa were calculated at the B3LYP/6-311G^＊ level using Gaussian 03 program. The isodesmic reactions were designed to calculate the standard free energy of formation （△fG^θ）. Three types of hydrogen bonds exist in the three kinds of chemicals and their bond energies were ascertained as 7-15, 15-23 and 49-58 kJ·mo1^-1 respectively by comparing the △fG^θ values. Electronic density topology analysis was applied to validate the strength of bond.

Electronic states and spin-filter effect in three-dimensional topological insulator Bi_2Se_3 nanoribbons

We study the electronic band structure, density distribution, and transport of a Bi2Se3 nanoribbon, We find that the density distribution of the surface states is dependent on not only the shape and size of the transverse cross section of the nanoribbon, but also the energy of the electron. We demonstrate that a transverse electric field can eliminate the coupling between surface states on the walls of the nanoribbon, remove the gap of the surface states, and restore the quantum spin Hall effects. In addition, we study the spin-dependent transport property of the surface states transmitting from top and bottom surfaces （x-y plane） to the side surfaces （z-x plane） of a Bi2Se3 nanoribbon. We find that transverse electric fields can open two surface channels for spin-up and -down Dirac electrons, and then switch off one channel for the spin-up Dirac electron. Our results may provide a simple way for the design of a spin filter based on topological insulator nanostructures.

Theoretical Studies on the Hydrogen Bonds of Different Position Action Mechanisms of Thymine with Uracil

In this research, the hydrogen bonds Y···H-X （X = C, N; Y = N, O） of thymine and uracil have been theoretically studied. The results show that hydrogen bond leads to bond length elongation and stretches the frequency red-shift of N-H···Y. Meanwhile, the C-H···O bonds shorten and stretch the frequency blue-shift. They all belong to traditional hydrogen bonds. The intermolecular charge transfer caused by the intermolecular hyperconjugation s＊（N–H） → n（Y） and intramolecular charge redistribution by intramolecular hyperconjugation σ（C-H） →σ＊（C-N） play important roles in the formation of hydrogen bonds. According to thejudgment standards proposed by Bader and Popelier, these hydrogen bonds have typical electron density topological properties. Electrostatic surface potential （ESP） is a useful physicochemical property of a molecule that provides insights into inter- and intramolecular associations, as well as the prediction of likely sites of electrophilic and nucleophilic metabolic attack.

AIM Study on the Reaction of CH2SH Radical with Fluorine Atom

The reaction of CH2SH radical with fluorine atom was studied at the levels of B3LYP/6-311G（d,p） and MP2（Full）/6-311G（d,p）. The computational results show that the reaction has three channels and proceeds by the addition of fluorine atoms on carbon or sulfur sites of CH2SH, forming initial intermediates. The calculated results show that the channel, in which fluorine attaches to the carbon atom to form CH2S and HF, is the most likely reaction pathway. Topological analysis of electron density was carried out for the three channels. The change trends of the chemical bonds on the reaction paths were discussed. The energy transition states and the structure transition regions （states） of the three channels were found. The calculated results show that the structure transition regions are broad in unobvious exothermic reactions or unobvious endothermic reactions, and are narrow in obvious exothermic reactions or obvious endothermic reactions.

Valley-dependent topological edge states in plasma photonic crystals

Plasma photonic crystals designed in this paper are composed of gas discharge tubes to control the flow of electromagnetic waves.The band structures calculated by the finite element method are consistent with the experimental results which have two distinct attenuation peaks in the ranges of 1-2.5 GHz and 5-6 GHz.Electromagnetic parameters of the plasma are extracted by the Nicolson-Ross-Weir method and effective medium theory.The measured electron density is between 1×1011 cm-3 and1×1012 cm-3,which verifies the correctness of the parameter used in the simulation,and the collision frequency is near 1.5×1010 Hz.As the band structures are corroborated by the measured scattering parameters,we introduce the concept of photonic topological insulator based on the quantum Valley Hall effect into the plasma photonic crystal.A valley-dependent plasma photonic crystal with hexagonal lattice is constructed,and the phase transition of the valley K(K’)occurs by breaking the spatial inversion symmetry.Valley-spin locked topological edge states are generated and excited by chiral sources.The frequency of the non-bulk state can be dynamically regulated by the electron density.This concept paves the way for novel,tunable topological edge states.More interestingly,the Dirac cone is broken when the electron density increases to 3.1×1012 cm-3,which distinguishes from the methods of applying a magnetic field and changing the symmetry of the point group.

三种同分异构的双苯并吩噻嗪材料的合成、理论计算及光物理性质

吩噻嗪及其衍生物材料是一类重要的多环芳烃材料,在光电子领域有着广泛的应用。其中,基于苯并噻嗪材料的研究相对较少。在本文中,我们分别在吩噻嗪的1,2-、2,3-和3,4-位引入苯基,制备了三种同分异构的双苯并吩噻嗪化合物D-PTZa、D-PTZb和D-PTZc,研究了它们的构效关系,并与双吩噻嗪化合物(D-PTZ)进行了对比。研究发现,D-PTZb和D-PTZc的HOMO和LUMO分布与D-PTZ的类似;对于D-PTZa,其1,2-位引入的苯基与中间的苯环空间张力较大,造成空间结构极度扭曲,性质比较特殊。并苯的引入可以有效增加分子的共轭长度,使得最大吸收波长发生红移;在2,3-位引入苯基可以有效地稳定HOMO能级,使基于π→π*跃迁的能隙稍有增大,呈现蓝光发射,溶液的荧光量子产率为1.7%;而在3,4-位引入苯基使LUMO分布更加趋向于线型,从而使LUMO更加稳定,使基于π→π*跃迁的能隙降低,其最大发射峰位于520 nm处,呈现黄绿光发射,溶液荧光量子产率为13%。此外并入苯环之后,空间张力增大,化合物的分解温度降低。我们的分子设计和结构–性质关系的研究可以为设计新的吩噻嗪材料提供基础指导。

团簇MnPS_(3)电子性质分析

为探究团簇MnPS_(3)的电子性质,设计出团簇MnPS_(3)模型,运用密度泛函理论,在B3LYP/def2-tzvp水平下对其进行优化处理,最终得到9种优化构型;利用原子电荷量、布居数以及电子自旋密度对团簇MnPS_(3)的电子性质进行综合分析。实验结果表明,由团簇MnPS_(3)布居数可知,电子主要由Mn原子的3d轨道、P原子的3s和3p轨道以及S原子的3s轨道流向剩余轨道;由团簇各原子的电荷量可知,Mn和P是电子的主要提供者,且Mn的失电子能力强于P,S则是电子的主要接受者;由团簇MnPS_(3)电子自旋密度可知,若原子间电子均匀分布以及原子间存在更多自旋向下的电子,则可能使团簇MnPS_(3)具有更良好的稳定性。

揭示配体拓扑结构对Fe-N_(x)-C单原子催化剂表面氧还原反应中间体吸附的影响

过渡金属单原子氮掺杂碳催化剂(TM-N-C SAC)因其更高的金属原子效率而被认为是提升氧还原反应(ORR)效率的重要途径.TM-N-C SAC反应中心的活性与配体结构密切相关,构建基于配体结构的ORR活性描述符是高效设计高催化活性单原子催化剂的关键.然而目前大多配体描述符基于催化剂的综合表观性质,如OH吸附能和金属中心d带中心等,其获取仍需进行额外计算,不利于通过配体结构快速推测反应活性;而目前基于配体结构拓扑参数,如金属中心原子及其配位原子属性、数量等设计的描述符存在对催化活性的描述较差或仅适用于特定配体等问题.解决该难题的关键在于理清OH与TM-N-C SAC成键的微观机制.本文全面考察了ORR中间体OH在21种具有不同氮原子数量、位置以及不同配体尺寸的卟啉型FeNxC SAC表面上的吸附机制.对有限尺寸卟啉型Fe-Nx-C(x=0-4)SAC模型上OH吸附的密度泛函理论计算结果表明,OH吸附能与SAC的配位氮原子的数量并不线性相关,且受氮原子排布方式的影响.利用能量分解分析(EDA)将OH与SAC的成键作用分解,重点讨论氮的掺入对静电作用、泡利排斥作用和轨道作用的影响.针对静电作用,Bader分析与电荷密度差值分析结果表明,氮的掺入一方面将电荷向配位原子上聚集,且配位原子上电荷数随氮原子数量增加而线性增加;另一方面大幅增强铁-配体键(Fe-L)的离子性,减少铁与配体间的电子密度,提高铁中心电子能量,并从而改变静电作用能量.对于泡利排斥作用,其影响因素与静电作用类似,因而作用强度与静电作用强度呈较好线性关系.对于轨道作用,结合扩展过渡态-化学价的自然轨道(ETS-NOCV)和电子定域化(LOL-π)等综合分析发现,氮原子的掺入破坏了配体的离域π键,从而影响OH与配体的轨道在成键时的相互作用.此外,对配体大小影响的研究表明,配体边缘原子仅当出现在包含配位原子的环上时才对OH与SAC成键有较大影响,这充分证明了OH吸附这一过程的局域性.综上,本文提供了Fe-N-C型SAC上完整的OH吸附键形成机制,强调了配位原子及其近邻原子对吸附活性的影响,为构建基于SAC拓扑特征的ORR活性描述符,实现SAC配体的快速筛选提供参考.

一种永磁吸附履带式爬壁机器人主体结构的变密度拓扑优化

针对爬壁机器人机身过重导致其运动灵活性差的问题,采用变密度法对爬壁机器人的主体结构进行拓扑优化,以降低机器人主体结构的质量。选择爬壁机器人主体结构质量占比大的关键部件进行变密度拓扑优化,并对优化结果进行有限元分析。分析结果表明,部件优化后结构最大变形量小于结构的许用变形量,最大静应力小于所用材料的许用强度,爬壁机器人主体结构质量由0.849 kg减少到0.673 kg,减轻了20.73%。

某机载电子设备轻量化设计研究

某型飞机严酷的载机环境对其列装的电子设备的重量和结构可靠性提出了更高要求。文中通过整机布局优化、功能模块整合、主承载结构优化的并行设计方法对机载电子设备开展减重设计,并进行了结构动力学仿真分析。结果表明,在满足结构力学性能基础上,减重设计后的设备质量降低了13%,并通过了随机振动、冲击等环境适应性试验。文中采用并行设计的方法,实现了电子设备轻量化设计,可供电子设备结构设计参考。

Theoretical Study on Hydrogen Interaction between 5-Fluorouracil and Glycine

The geometries,electronic structure,IR spectrum and other properties of hydrogen interaction between 5-fluorouracil and glycine were studied at the B3LYP/6-31＋G＊ level.Single point energy calculations were executed at the B3LYP/6-311＋＋G＊＊ and B3LYP/aug-cc-pvdz levels,and natural bond orbital （NBO） analysis was carried out at the B3LYP/6-31＋G＊ level.Finally,the hydrogen bonds were discussed via AIM electronic density topology analysis.

Effects of electromagnetic radiation on spatial memory and synapses in rat hippocampal CA1

In this study, we investigated the effects of mobile phone radiation on spatial learning, reference memory, and morphology in related brain regions. After the near-field radiation （0.52 1.08 W/kg） was delivered to 8-week-old Wistar rats 2 hours per day for 1 month, behavioral changes were examined using the Morris water maze. Compared with the sham-irradiated rats, the irradiated rats exhibited impaired performance. Morphological changes were investigated by examining synaptic ultrastructural changes in the hippocampus. Using the physical dissector technique, the number of pyramidal neurons, the synaptic profiles, and the length of postsynaptic densities in the CA1 region were quantified stereologically. The morphological changes included mitochondrial degenerations, fewer synapses, and shorter postsynaptic densities in the radiated rats. These findings indicate that mobile phone radiation can significantly impair spatial learning and reference memory and induce morphological changes in the hippocampal CA1 region.

Density Functional Studies on Isonicotinato Lead(II) Complex [Pb(C_5H_4NCOO)_2]

The title compound of isonicotinato lead（Ⅱ） [Pb（C5H4NCOO）2] has been optimized at B3LYP/LANL2DZ level of theory and calculated results show that the lead（Ⅱ） ion adopts 4-coordinate geometry. Atomic charge distributions indicate that during forming the title compound, each isonicotinic acid ion transfers -0.452 e to lead（Ⅱ） ion. The electronic spectra calculations show that there exist two absorption bands and the electronic transitions are mainly derived from the contribution of intraligand π→π^＊ transition and ligand-to-metal charge transfer （LMCT） transition. The thermodynamic properties of the title compound at different temperatures have been calculated and corresponding relations between property and temperature have also been obtained. The calculation of the second order optical nonlinearity was carried out, and the molecular hyperpolarizability was 3.62365^＊10^-30 esu.

基于SIMP变密度法的工业机器人大臂拓扑优化设计

以某工业机器人机械大臂为研究对象,基于SIMP变密度法的拓扑优化数学模型思想,先使用ADAMS软件获得机器人大臂在最劣工况下的载荷情况,然后通过Altair Inspire软件,设置机器人大臂最劣工况载荷,对原始模型进行有限元分析,并以最大化刚度为优化目标,完成了机器人大臂的拓扑优化设计。通过对机器人大臂各种优化方案的对比,结果表明,在满足机器人大臂载荷、空间要求和刚度要求的前提下,减重率达26.28%,达到了机器人大臂轻量化设计的目的,并为相关结构件轻量化设计提供了参考。

桥式起重机主梁结构的可靠性拓扑优化

为了在降低设计难度和提高设计效率前提下实现起重机主梁结构的可靠性优化设计,首先基于变密度方法和概率方法分别构建以起重机主梁结构体积最小作为目标函数的确定性拓扑优化模型和可靠性拓扑优化模型;其次,将可靠性拓扑优化模型中的优化问题经混合法解耦处理后,分解为可靠性分析和当量确定性拓扑优化2个独立子问题;再次,在优化设计过程中使用灰色关联系数法分配各工况的权重系数;最后,再对经过可靠性拓扑优化设计后所得的新型主梁结构进行二次设计。结果表明,同确定性拓扑优化比较,可靠性拓扑优化的迭代次数较少,计算速度较快;经二次设计后,起重机主梁结构的刚度、强度与固有频率均得到了提高;设计结果可为起重机金属结构优化设计提供新思路。