简单共轭体系的共振结构和前线轨道的对应关系

<正> 量子力学处理共轭分子的两种近似理论——价键法(VB法)和分子轨道法(MO法)——分别由L.Pauling[1]和E.Huckel[2]于本世纪三十年代初提出。前者把基态分子波函当作各可能价键结构波函的线性组合,即:     

Fapy-G对碱基氢键复合物影响的理论研究

应用量子化学方法对2,6-二氨基-4-羟基-5-甲酰胺嘧啶(Fapy-G)与正常碱基作用形成的20种氧化碱基对的多种性质进行了理论分析,碱基G的C8位被氧化后N7和N9位分别增加一个H原子,使其由氢键受体变成氢键供体,N7,N9及O6原子所带的电荷变负,同时O6作为氢键受体的能力增强.与碱基单体相比,碱基对中形成氢键的受体原子所带的电荷平均减小0.05 e;供体H原子所带的电荷平均增大0.02 e.Fapy-G分子中六元环上受体N原子参与形成氢键时,环的呼吸振动模式和N与对位C的振动模式的振动频率蓝移;与氢键相关的振动频率红移.所有氧化碱基对中,NH…N比NH…O氢键作用更强,且在NH…N氢键中,在六元环上的供体N原子形成的氢键比在氨基或开环上的供体N原子形成的氢键强.Fapy-G与碱基A作用结合能区域顺序为1>2>4>3,与碱基T(R)作用区域顺序为3=4>1>2;水溶液使Fapy-G与碱基C作用的结合能减弱程度最大,结合能达到41.84~58.58 k J/mol,且使碱基对结合能力次序发生改变.     

静电平衡时导体上电荷的分布初探

在高中物理教材对电荷分布阐述的基础上进行扩展,用高斯定理对静电平衡状态下导体上净电荷分布进行一些分析.     

轴对称电荷分布非静态轴外场的一种计算方法

利用麦克斯韦方程组和轴对称性,给出了轴对称电荷分布非静态轴外场的一种计算方法.     

Exploring the light-quark interaction

Two basic motivations for an upgraded JLab facility are the needs： to determine the essential nature of light-quark confinement and dynamical chiral symmetry breaking （DCSB）; and to understand nucleon structure and spectroscopy in terms of QCD＇s elementary degrees of freedom. During the next ten years a programme of experiment and theory will be conducted that can address these questions. We present a Dyson- Schwinger equation perspective on this effort with numerous illustrations, amongst them： an interpretation of string~breaking; a symmetry-preserving truncation for mesons; the nucleon＇s strangeness σ-term; and the neutron＇s charge distribution.     

Studies of Solvent Effects on Structure and Low Frequency Vibrational Spectra of 2,4-Dinitrotoluene

Solvent effects on 2,4-dinitrotoluene(2,4-DNT) molecule in different solvents(toluene,ethanol,and water) were studied via DFT PCM method at B3LYP/6-311+G(d,p) level. The influences of these solvents on the molecular structure,vibrational spectra,charge distribution,and dipole moment were studied as well. The results show that PCM computations are successful in describing the vibrational spectra of 2,4-DNT molecules in these solutions and the solvent effects on the low frequency vibrational spectra are weak.     

Analysis of Charge State Distribution by Non-Local Thermodynamic-Equilibrium Spin-Orbit-Split-Array Collisional Radiative Model

A collisional radiative model based on the spin-orbit-split-arrays is used to determine the charge state distribution of gold plasmas. The ab initio atomic structure code of Cowan and the spin-orbit-split-array model were used to calculate all the emission spectra of the different gold species, and a non-local thermodynamic-equilibrium model was coupled to calculate the ion populations at a given plasma density and electron temperature. The charge state distribution and other plasma parameters were determined by comparing the experimental spectra with the theoretical simulated soectra of gold plasmas.     

分子中电荷分布的原子点电荷模型：势诱导法计算原子点电荷

自从知道分子是由原子组成,而原子是由带正电的核及带负电的核外电子组成后,便有分子中电荷分布的原子点电荷模型:即在分子中某些原子上带适量的正电荷,而在另一些原子上则带适量的负电荷。但是,随着人们对客观事物的进一步认识,和有了描述微观粒子运动的量子力学后,得知分子中电荷分布的实际情况要复杂得多:正电荷集中在各原子核上,而带负电的一部分内层电子虽仍围绕着原来的原子核运动,但另一部分原来各原子的外层价电子     

导体表面的电荷分布

从对称性角度出发讨论了导体表面的电荷分布问题，并对“电荷密度分布函数”的理论作了评述。