不同电子组态下镧系元素的轨道指数和电负性

用Xa方法计算出不同电子组态下镧系元素的数值原子轨道和轨道电负性,用数值拟合方法得出原子轨道的单ζ和双ζSlater型基函数的指数。研究了镧系元素原子所带电荷与电子组态对其原子轨道指数与轨道电负性的影响,给出了精确度较高的回归公式。这些公式能反映原子轨道性质变化的规律,且能提供为研究镧系元素化合物的电子结构的基础参数和电荷自洽型计算的迭代公式。     

分子体系的高压化学反应

在高压(一万到百万大气压)下物质的组成、结构、化学反应都可以发生前所未知的巨大变化。运用高压合成目标产物,表征高压下的物质结构与反应过程是高压化学研究的主要问题。一般而言,高压下不饱和化合物倾向于聚合形成高密度饱和共价键体系;反应中分子与原子扩散严重受限,常形成亚稳态化合物;反应物的空间晶体结构、官能团性质、反应体系的温度、静水压效果都对反应有显著影响。对高压下分子化学反应的研究需要综合运用晶体学、谱学、化学等实验手段和热力学、动力学等方面的理论计算相互验证,进而建立理论,深入极端条件化学的星辰大海。     

稀土高压化学

稀土元素因其丰富的电子结构,表现出很多独特的物理化学性能,在光学、磁性和电学等领域具有巨大的应用价值。压力作为自然界中基本的热力学变量,可以引起结构相变以及新的亚稳态稀土化合物的合成,高压下稀土元素及其化合物表现出许多新奇的物理化学性能,如室温超导、铁磁半金属等。简要概述稀土元素及其化合物高压研究进展,包括压致相变、化学合成等,以及高压对其磁性、光学等物理性质的影响,展示了高压化学在稀土领域的应用前景。     

周期表中的相对论性效应

随着原子序数增大而迅速增强的相对论性效应是决定重元素及其化合物“反常”化学性质的重要因素。因此,我们在研究众多的化学现象时,不能忽略这一重要因素。本文试用原子轨道的主要相对论性效应来解释元素周期表中的一些“反常”现象。     

中性原子的轨道能量

在化学教学中,当讨论到原子的核外电子排布时,我们需要知道1s,2s,2p,3s,3p,3d,4s,…直至7s等原子轨道的能量随原子序数z变化的情况。Cotton和     

电离能和原子轨道能的关系

在教学过程中,常发现同学对电离能I和按Slater屏蔽系数法计算的原子轨道能量 E=-（（Z-σ）2/n2）R （1）区分不清,误认为电离掉某一电子所需要的能量即电离能I就是按式（1）计算的这个电子所处原子轨道能量E的负值。     

对原子轨道图形教学的意见

原子轨道(又称原子轨函)的图形和电子云分布的图形是化学教学中的基本内容,是了解原子结构的关键之一。在教学中正确地表达这两种图形,是化学教学的重要一环。通常原子轨道图形由在原子核周围空间原子轨道ψ的等值线图形表示。在二维平面上作图时,常选择通过原子核和两个坐标轴的平面,在这平面上画出等值线。图1示出几种原子轨道的等值线图。     

重要生物微量元素和常见负电性元素在不同价态和电子组态下的轨道指数和电负性

本文用Xα方法计算出不同价态与电子组态下锰、铁、钴、铜、锌及钼等过渡族重要生物微量元素和氮、氧、氟、磷、硫、氯、硒和溴等常见负电性元素的数值原子轨道和轨道电负性值,再用数值拟合方法得出这些原子轨道的单ξ和双ξSlater型基函数的指数.研究了这些元素的原子所带电荷和电子组态对其原子轨道指数与轨道电负性的影响,给出了相应的回归公式.这些公式有较高的精确度,不但为研究这些元素化合物的电子结构提供基础参数,也为电荷自洽型的计算提供较可靠的计算公式.     

重要生物微量元素和常见负电性元素在不同价态和电子组态下的轨道指数和电负性

本文用Xα方法计算出不同价态与电子组态下锰、铁、钴、铜、锌及钼等过渡族重要生物微量元素和氮、氧、氟、磷、硫、氯、硒和溴等常见负电性元素的数值原子轨道和轨道(?)负性值,再用数值拟合方法得出这些原子轨道的单ξ和双ξSlater型基函数的指数.研究了这些元素的原子所带电荷和电子组态对其原子轨道指数与轨道电负性的影响,给出了相应的回归公式.这些公式有较高的精确度,不但为研究这些元素化合物的电子结构提供基础参数,也为电荷自洽型的计算提供较可靠的计算公式.     

轨道和波函数

分子（或原子）轨道是化学的基本概念之一。本文从Bohr原子轨道入手,介绍轨道概念的演化,以及轨道与波函数之间的关系,分子轨道与原子轨道之间的关系,并结合量化计算介绍基组与分子轨道的关系。     

有机二硫化物润滑添加剂抗磨极压性能的密度泛函理论研究

用量子化学的密度泛函理论计算了12种有机二硫化物和铁原子簇的分子轨道指数及其与铁原子簇的化学吸附作用能, 探讨了这种作用能与抗磨性能的关系; 运用轨道能量近似原则讨论了有机二硫化物与铁原子的作用方式; 以前线电子密度、超离域性指数和原子净电荷作为判据分析了12种有机二硫化物与铁原子间键合的强弱、反应性的大小等表征有机二硫化物与金属作用强弱的参数。结果表明: 有机二硫化物与铁接触时, 在较缓和条件下, SS键优先断裂与金属发生化学吸附形成配位键, 起到抗磨作用; 在高负荷下, 与金属发生常规条件下不能发生的化学反应, 即CS键断裂生成无机膜, 起到极压作用; 且随着碳链的增长, 有机二硫化物的抗磨性能愈来愈好, 但极压性能愈来愈差; 运用量子化学计算得到的预测结果与摩擦学试验结果具有良好的一致性, 可为同类极压添加剂化合物的分子设计提供较为可靠的参考依据和理论方法。     

二苯二硫和二苄二硫润滑性能的量子化学研究

The molecular geometries optimization and electronic structures of diphenyl disulfide (DPDS) and dibenzyl disulfide (DBDS) compounds were investigated by density functional theory (DFT) and ab initio method at the 6-31G basis set level. The active atoms and bonds of reaction were provided by frontier molecular orbital theory. The molecular orbital parameters of DPDS and DBDS compounds and iron atom cluster were calculated by using density functional theory. The interaction pattern between the organic disulfide compounds and iron atom cluster was discussed based on the approximate rule of orbital energy. Some parameters characterizing the action strength between the organic disulfide compounds and iron atom cluster, including the bonding strength, reactive strength and static action strength, were analyzed by using frontier electron density, super de-localizability, net atomic charge and the interaction energy of chemical adsorption as criteria. The results indicate that S-S chemical bond and C-S chemical bond of the compounds are inclined to be broken when DPDS and DBDS interact with the metal. The anti wear ability order of DPDS and DBDS compounds is DPDS>DBDS, and the extreme pressure ability order of DPDS and DBDS compounds is DBDS>DPDS, and the prediction results based on quantum chemistry calculations are in good accordance with the friction and wear test results.     

Surface facetting induced by adsorbates

The presence of adsorbates can modify the morphology of the underlying substrate. The modifications are the results of a subtle thermodynamic balance between intermolecular and molecular-substrate interactions together with the surface relaxation energy. The information on how the substrate structures are influenced by the adsorbates, and therefore, the physical and chemical properties of the resulting interface is fundamentally important. In this review, we examine facetting of transition metals induced by either atomic species or organic molecules. First we focus on facetting induced by atomic species and small molecules under high pressure or UHV conditions. Following that, organic molecules containing several electronegative elements, such as amino acids, benzoic acid and aminobenzoic acid, are examined. These organic molecules can induce large scale facets with great similarity on fcc crystal surfaces. Learning from the correlation between the facetting induced by these molecules and those of atomic species, we try to rationalise the molecular mechanism for the formation of adsorbate induced facets.     

几种吡啶-4-甲酰胺噁二唑化合物的合成及其紫外吸收和电化学性质

合成了四个2-吡啶-4-甲酰胺基-5-芳香基-1,3,4-噁二唑化合物,利用紫外吸收光谱法和循环伏安法研究了化合物的紫外吸收和电化学性质,并对其进行了量子化学计算.结果表明,四种化合物的紫外吸收图谱非常相似,并且在电极上发生不可逆的氧化还原过程.利用量子化学计算确定化合物的稳定结构及前线轨道能量,在理论上对化合物的性质加以解释.     

Bismuth nanowires for potential applications in nanoscale electronics technology.

Nanowires of bismuth with diameters ranging from 10 to 200 nm and lengths of 50 microm have been synthesized by a pressure injection method. Nanostructural and chemical compositional studies using environmental and high resolution transmission electron microscopy with electron stimulated energy dispersive X-ray spectroscopy have revealed essentially single crystal nanowires. The high resolution studies have shown that the nanowires contain amorphous Bi-oxide layers of a few nanometers on the surface. In situ environmental high resolution transmission electron microscopy (environmental-HRTEM) studies at the atomic level, in controlled hydrogen and other reducing gas environments at high temperatures demonstrate that gas reduction can be successfully applied to remove th oxide nanolayers and to maintain the dimensional and structural uniformity of the nanowires, which is key to attaining low electrical contact resistance.     

Structure prediction of high-pressure phases for alkali metal sulfides

For a given chemical system we present a systematic approach to predict structures, which may exist at high pressure, by investigating the global enthalpy landscape. We combine global optimizations, based on empirical potential energy functions, and local optimizations (volume, cell shape, and atomic positions) on both Hartree-Fock and density functional theory level. We predict the existence of high-pressure phases for the alkali metal sulfides of the composition M2S (M = Li, Na, K, Rb, Cs), together with the transition pressures among these phases.     

Electronic Transitions in Transition Metal Compounds at High Pressure

Very high pressure is becoming increasingly important for investigating electronic structure. The relative shift in energy of electronic orbitals which is commonly observed at high pressure can frequently lead to a new ground state for the system. These electronic transitions may result in changes in electrical, optical, or magnetic properties as well as changes in chemical reactivity. Electronic transitions in metals and insulator-metal transitions have been widely studied by physicists. Recently, it has been found that electronic transitions in aromatic hydrocarbons and their electron donor-acceptor complexes can induce chemical reactivity and lead to the formation of new classes of hydrocarbons. Electronic transitions in transition metal complexes may lead to changes in spin state; both increase and decrease in multiplicity with increasing pressure have been observed. In addition, it has been shown that Fe(III ) and Cu(II ) reduce at high pressure in a variety of compounds. The behavior of these transition metal ions is described in some detail in relation to the general area of high pressure and electronic structure.     

论化学学习中的能量观建构

能量观是中学化学学习中的核心观念。能量观的建构有利于学生形成核外电子运动的能量思维方式,了解从能量的角度研究物质及其转化的思维方法等。能量观建构的基本策略是:(1)在物质的微粒性认识学习中形成物质的微粒具有热能的观念;(2)在原子结构学习中形成核外电子运动的能量思维方式;(3)在元素及其化合物学习中发展高能量的最外层电子不稳定的认识;(4)在化学变化现象的积累学习中强化物质转化伴随有能量变化的认识;(5)通过化学键概念及其理论学习理解物质转化过程中伴随有能量变化;(6)在影响化学反应速率的条件讨论中深化理解有效碰撞理论;(7)在化学热力学问题研究中进一步理解能量守恒;(8)利用概念图技术帮助化学能量观的建构。     

Determination of atomic hydrogen in non-thermal hydrogen plasmas by means of molecular beam threshold ionization mass spectrometry

Atomic hydrogen plays important roles in chemical vapor deposition of functional materials, plasma etching and new approaches to chemical synthesis of hydrogen-containing compounds. The present work reports experimental determinations of atomic hydrogen near the grounded electrode in medium-pressure dielectric barrier discharge hydrogen plasmas by means of molecular beam threshold ionization mass spectrometry (MB-TIMS). At certain discharge conditions (a.c. frequency of 24 kHz, 28 kV of peak-to-peak voltage), the measured hydrogen dissociation fraction is decreased from approximately 0.83% to approximately 0.14% as the hydrogen pressure increases from 2.0 to 14.0 Torr. A simulation method for extraction of the approximate electron beam energy distribution function in the mass spectrometer ionizer and a semi-quantitative approach to calibrate the mass discrimination effect caused by the supersonic beam formation and the mass spectrometer measurement are reported.     

Chemical and Physical Solutions for Hydrogen Storage

Hydrogen is a promising energy carrier in future energy systems. However, storage of hydrogen is a substantial challenge, especially for applications in vehicles with fuel cells that use proton‐exchange membranes (PEMs). Different methods for hydrogen storage are discussed, including high‐pressure and cryogenic‐liquid storage, adsorptive storage on high‐surface‐area adsorbents, chemical storage in metal hydrides and complex hydrides, and storage in boranes. For the latter chemical solutions, reversible options and hydrolytic release of hydrogen with off‐board regeneration are both possible. Reforming of liquid hydrogen‐containing compounds is also a possible means of hydrogen generation. The advantages and disadvantages of the different systems are compared.