Computational study on the reaction CH2CH2 + F --> CH2CHF + H

Previous ab initio studies on reactions involving radical addition to alkenes showed that such reactions are very sensitive to theoretical levels, and thus are difficult to deal with. This motivates us to theoretically reexamine the title reaction thoroughly, which has been studied only at several low levels of theory. In the present work, the geometry optimizations and energy calculations for all species involved in the title reaction were performed at several high levels of theory. The reaction mechanism of the title reaction is discussed at the CCSD(T)/aug-cc-pVDZ//CCSD/6-31G(d,p) theoretical level. According to our study, the fluorine addition to ethylene occurs via the formation of a prereaction complex with C2v symmetry, which is pointed out for the first time. The prereaction complex evolves into a fluoroethyl radical almost without a barrier, with an exothermicity of 41.49 kcal/mol. The fluoroethyl radical can further decompose into a hydrogen atom and fluoroethylene, with an energy release of 10.33 kcal/mol. Besides the direct departure of the hydrogen atom from the fluoroethyl radical, an indirect decomposition pathway may also be open, which has not been reported before. In addition, the formation of a fluoroethyl radical from a separate fluorine atom and ethylene is described pictorially via the molecular intrinsic characteristic contour (MICC) and the electron density mapped on it. Thereby, strong interpolarization and evident electron transfer between the fluorine atom and ethylene are observed as they approach each other. The transition structure for the fluorine addition to ethylene is clearly shown to be reactant-like. This provides new and intuitional insight into the title reaction.     

应用分子形貌理论研究类SN2反应

应用分子形貌理论, 研究了类SN2反应过程中的沿着IRC路径上固定点的分子形貌的特征, 计算给出了形状和电子密度特征参数以及各键的Dpb值. 应用Matlab程序绘制了分子特征边界轮廓上的电子密度分布的三维图像, 即分子形貌像, 给出了这类反应的动态变化过程.     

On the Convergence of the Factorization Update Algorithm

In this paper, we make a Kantorovich-type analysis for the spares Johnson and Austria's algorithm given in [2], which is called factorization update algorithm. When the mapping is linear, it is shown that a modification of that algorithm leads to global and Q-superlinear convergence. Finally, we point out the modification is also of local and Q-superlinear convergence for nonlinear systems of equations and give its corresponding Kantorovich-type convergence result.     

杂原子取代卟啉的电子结构和光谱

用INDO/CI法计算了等电子氧杂、硫杂、氮杂卟啉的电子结构及低激发态电子跃迁.从前线轨道特征、电荷分布等与自由卟啉对比讨论了杂原子取代卟啉的电子结构.计算结果还预期了一些杂原子取代卟啉的低激发态电子跃迁光谱.     

H2X(X=O,S)分子简正模激发态下分子内能量转移的研究

采用准经典轨迹法,考察了H₂O及H₂S分子简正模激发态下分子内各态能量随时间变化的分布关系,讨论了激发能在各态间的转移规律.研究表明:简正模激发态能量转移倾向于频率彼此相近或对称性相同的态间.     

Computing eigenpairs of Hermitian matrices in perfect Krylov subspaces

Numerical Algorithms - For computing the smallest eigenvalue and the corresponding eigenvector of a Hermitian matrix, by introducing a concept of perfect Krylov subspace, we propose a class of...     

ABEEM/MM浮动电荷力场应用于血红素结构的研究

运用拟合的参数, 应用ABEEM/MM浮动电荷力场对血红素分子结构进行了模拟. 结果表明, 该力场与CHARMM力场相比, 能更好地模拟晶体结构. 计算的ruffing构象能与B3LYP/6-31G*计算结果的线性相关系数在0.98以上, 同时表明血红素分子中twist-angle对ruffing构象具有明显影响. ABEEM/MM力场计算的细胞色素c552中血红素分子的电荷分布与CHARMM固定电荷力场的比较, 更准确地反映了血红素分子的电荷分布以及极化现象.     

Identification of 11 Marker Compounds Simultaneously in Herb Lancea tibetica by Using High-Performance Thin-Layer Chromatography

JPC – Journal of Planar Chromatography – Modern TLC - A high-performance thin-layer chromatography (HPTLC) method was developed for simple and rapid chemical analysis of Lancea tibetica...