弱Hopf群余代数Kegel定理

本文研究了余三角弱Hopfπ-余代数H的左弱π-H-余模代数.通过构造左弱π-H-余模代数的导出π-σ-李代数,得到了弱Hopf π-余代数Kegel定理,推广了文献[4]的结果.     

独立存在的π单键

化学中的共价键分为两类，σ键和π键。σ键可以独立存在，也可以和π键同时存在于多重键中，而对于π键而言，目前教科书中介绍的都是与σ键共存的情况。但是π单键是否可以独立存在呢？虽然可供参考的文献很少，但近期的科研成果表明π单键是可以独立存在的。本文围绕近年来可独立存在π单键的研究进展和特点进行简要综述。     

焊后热处理对聚变堆用奥氏体不锈钢MAG焊焊缝金属冲击韧性的影响

After heat treatment of metal active gas arc welding (MAG weld) joints of 316LN austenitic stainless steel for fusion reactor at different temperatures, Charpy impact test at liquid nitrogen temperature was carried out. The effects of heat treatment temperature on microstructure, fracture morphology and precipitates were studied with optical microscope, SEM and EDS analysis. Results indicated that the impact toughness of weld metal could be significantly improved by 873K heat treatment. However, with the rising of heat treatment temperature, the precipitates were generated gradually along the grain boundary and a gradual decrease of toughness occurred as well. All fracture was ductile. The dimple became shallow and less with the increase of temperature. Spherical and irregular precipitates were found at the bottom of the dimple. The spherical precipitates generated during welding were free from the influence of the heat treatment, and the irregular precipitates increased with the rising of temperature. High content of Mo in filler materials led to a great segregation of Mo at the grain boundary, which would promote the precipitation of σ phase. Impact toughness of weld metal decreased significantly when continuous distribution of σ phase formed at grain boundary.     

Proton Transfer Isomerization of Pyrazole in the Ground State： σ vs π Mechanism and Water Assisting Effect

The proton transfer isomerization of pyrazole and the water assisting effect by looping 1 to 4 water molecules on the singlet state potential energy surface have been investigated by using hybrid density functional theory method （B3PW91） with a 6-311＋＋G^＊＊ basis set. Two mechanisms were proposed to explain the mono- and multi-water assisting effects, respectively. The reactants and products of all groups have been characterized on their potential energy surfaces. For the isomerizafion of monomolecule pyrazole, the isomeriz＇ation energy barrier is 46.4 kcal·mol^-1. For the monohydration assisting mechanism, the reactant complex is connected to the product complex via two saddle points. The corresponding isomerization barriers are 46.7and 23.0 kcal·mol^-1, respectively. As to the multihydration assisting mechanism, the isomerization barriers are 12.0, 10.9 and 13.14 kcal·mol^-1 accordingly, when the number of water molecules is 2, 3 and 4, respectively. The multihydration assisting isomerization can occur in water-dominated environments, for example, in the organism, and thereby is crucial to energy transference. The deproton and dehydrogen energies of monomolecule pyrazole and various hydrated pyrazoles were calculated and then found much bigger than the isomerization barriers of their relative complexes, suggesting the impossibility of deprotonation or dehydrogenation. The isomerization of pyrazole is a proton-coupling-electron-migration process, but two different mechanisms are noticed, viz. σ- and π-type mechanisms. The π-bond of pyrazole participates in isomerization in the π-type mechanism, whereas only o-electron takes part in isomerization in the σ-type mechanism.     

杂化轨道成键能力及夹角计算公式的简洁推导

杂化轨道理论是化学键理论的重要内容,杂化轨道成键能力和杂化轨道之间的夹角是杂化轨道理论教学的重点和难点,多数教材通常直接给出相关公式,忽略导出过程,不能满足部分学生进阶学习的需要。本文给出了相关公式的简易推导,以期解疑释惑,加深学生对杂化轨道理论的认识和理解。     

卤代硅烷(R3SiX)与NR'3形成五配位硅化合物的加成反应

对R3SiX(R=H、CH3;X=F、Cl、Br、I)与NR'3(R'=H、CH3)的加成物用量子化学密度泛函方法在B3LYP/6-31g(d,p)基组下(X原子采用cep-121g基组)进行了两种加成方式的研究.一种是NR'3沿Si-X键轴向位置的加成,另一种是NR'3沿Si-X键侧向接近的加成.计算结果表明,前者更稳定且更容易形成加成物;Si上斥电子基团不利于Si-N键的形成,而N上斥电子基团则有利于Si-N键的形成;NH3-H3SiX系列和N(CH3)H3-H3SiX系列均能以两种方式进行加成,NH3-H2(CH3)SiX系列仅能沿Si-X键轴向进行加成,而NH3H(CH3)2SiX和NH3-(CH3)3SiX系列两种方式都不能进行加成;在同系列加成产物中,以X=Cl时所得加成物最稳定.讨论了所有加成物中各键的性能、NBO电荷变化、取代基对加成物结构和稳定性的影响,并对H3SiX(X=F、Cl、Br、D与NH3及N(CH3)3加成物在有机溶剂中导电的可能性进行了讨论.     

C_4S_4~(m-)(m=0,1,2,3,4)的从头算研究2.成键状况、电离势和振动频率

在ＲＨＦ（基离子在ＵＨＦ）／６－３１Ｇ,６－３１Ｇ＊和６－３１＋Ｇ水平用从头算和Ｂｏｙｓ定域化方法计算了Ｃ４Ｓ４ｍ－（ｍ＝０,１,２,３,４）的电子结构、电离势和定域化分子轨道。讨论了其成键特征和电离势与ΔＥＳＣＦ的关系。在６－３１Ｇ水平用ａｂｉｎｉｔｉｏ解析方法计算它们的谐振动频率。电子结构计算结果和Ｂｏｙｓ定域化分子轨道及振动分析结果与优化的平衡几何和相对稳定性相一致     

C4Om-4(m=0,1,2,3,4)的从头算研究 2.化学键、电离势和振动频率

在第1报优化的几何构型的基础上,用Boys定域化方法和QSU90程序计算了C4Om-4(m=0,1,2,3,4)的定域化分子轨道,讨论了其成键特征和电离势.在6-31G水平用ab initio解析方法计算它们的谐振动频率.     

半序线性空间中混合单调映射不动点的存在唯一性

本文研究半序线性空间中一类混合单调映射不动点的存在唯一性及其迭代方法,对所述映射没作连续性或紧性假定．其推论改进了序Banach空间中增算子与减算子的某些已知结果．最后把所得结论用于常微分方程奇异边值问题．     

4f轨道的成键性质

本文介绍了目前国内外关于镧系配合物４ｆ轨道成键行为研究的现状与进展,对其理论和研究方法进行了系统的总结,归纳了４ｆ轨道的成键规律。