量子化学从头计算法研究C~8~4的分子静电势

取价层双ζ基(7s4p)/[3s2p]从头计算法优化的分子几何构型, 在Hartree-Fock/6-31G水平, 分别计算了Fullerene C~8~4的D~2~d和D~2点群对称性的两种稳定异构体的分子静电势, 获得了过C~8~4对称中心的三个正交平面XY, XZ和YZ上的平面静电势图和径向静电势图, 并与其它Fullerene的静电势做了比较。     

TinC2n(n=1-6)分子簇的量子化学从头算研究

用量子化学从头计算方法研究了TinC2n(n=1-6)分子簇的几何构型和电子结构。这些TinC2n分子簇以TiC2为结构单元, 通过C-C或Ti-C键进一步连接而逐渐长大。研究结果可以较好地解释实验现象, 并说明Metcars的形成机理。     

银表面甲醇氧化反应机理的ab initio计算研究 1: 银表面静态吸附物种的几何构型和吸附性质

本文用原子簇模型(CM)的从头计算方法, 计算了银表面甲醇氧化反应中的静态吸附物种的优化几何构型及吸附性质。计算表明在清洁银表面甲醇、甲醛只存在物理吸附; 当表面存在吸附氧原子时, 甲醇可在银表面形成两种分子态吸附;甲醛与表面羟基OH(a)或氢原子H(a)共存时在银表面能够形成化学吸附, 且CH2O(a)极易与O(a)反应生成深度氧化中间体η^2-甲二氧基; 中间产物甲氧基在无氧的银表面能够形成稳定吸附, 在富氧银表面极易进一步氧化脱氢生成产物甲醛。通过计算与实验结果的对照, 我们对反应机理作了初步讨论。     

Preparation of block copolymers of polystyrene and poly (t‐butyl acrylate) of various molecular weights and architectures by atom transfer radical polymerization

Block copolymers of polystyrene and poly(t‐butyl acrylate) were prepared using atom transfer radical polymerization techniques. These polymers were synthesized with a CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine catalyst system and had predictable molecular weights based on the degree of polymerization, as calculated from the initial ratio of monomer to initiator. The final polydispersities were low (1.10 < M_w /M_n < 1.3) for all the homopolymers and block copolymers. Polymers of various chain architectures were prepared, ranging from linear AB diblocks to three‐armed stars composed of AB diblocks on each arm. The key to controlled synthesis with this catalyst system was the choice of the solvent, temperature, and concentrations of catalyst and deactivator. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2274–2283, 2000     

Stabilization of Infinite-Dimensional Semilinear Systems with Dissipative Drift

In this paper we study feedback stabilization for distributed semilinear control systems . Here, A is the infinitesimal generator of a linear C ₀ -semigroup of contractions on a real Hilbert space H and is a nonlinear operator on H into itself. A sufficient ad-condition is provided for strong feedback stabilization. The result is illustrated by means of partial differential systems. Accepted 31 July 1996     

Immobilization of manganese peroxidase fromLentinula edodes on alkylaminated emphazeTM AB 1 polymer for generation of Mn3+ as an oxidizing agent

Manganese peroxidase (MnP) is secreted by white-rot fungi and participates in the degradation of lignin by these organisms. MnP uses H₂O₂ as an oxidant to oxidize Mn^II to Mn^III as the manganic ion Mn³⁺. The Mn³⁺ stabilized by chelation, is a highly reactive nonspecific oxidant capable of oxidizing a variety of toxic organic compounds. Previous attempts at immobilization of MnP, purified fromLentinula edodes through reactive amino groups, have been hindered by the protein’s low lysine content of only 1% and its instability above pH 6.0. As an alternative to amine coupling, the enzyme has now been covalently immobilized through its carboxyl groups, using an azlactonefunctional copolymer derivatized with ethylenediamine and 2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline (EEDQ) as a coupling reagent. The immobilization reaction was performed under acidic (pH 5.25) conditions, and 90% coupling efficiency was achieved within 2 h. Net immobilization efficiencies, expressed as the product of protein coupling efficiency and enzyme activity, have been measured at > 95% within 4 h. The MnP-NH-polymer and the free soluble protein were characterized and compared for their pH, temperature, and storage stabilities, as well as their H₂O₂ dependence and kinetics. The tethered MnP, employed in an immobilized enzyme bioreactor for generation of chelated Mn₃₊ may have industrial applications as a nonspecific oxidant of organopollutants.     

甲基环丙烷卡宾重排反应机理的探讨

本文用HF/STO-3G解析梯度方法计算了甲基环丙烷卡宾重排反应的8个构型,它们代表4个反应类型.计算结果表明,甲基的H原子对卡宾碳的1,3迁移遵从端端告拢机理.环丙烷上的H原子1,2迁移活性遵从夹有相似文献   

平面型1,1-二锂代环丙烷比四面体型稳定的原因

在3-21G/Dunning基水平的量子化学"从头计算"基础上,绘制平面型1,1-二锂代环丙烷(PDCP)的A~1及B~2对称块中各分子轨道的波函数等值线图及PDCP和TDCP (四面体型)B~1和A~2对称块中各分子轨道示意图,并且求出PDCP及TDCP中各价电子i对于各种键A-B的f~i,A-B值.得到结论:由f~i,A-B所得定量结论与上述两种图形所得定性结论是完全一致的.再一次证明用f~i,A-B定量表达i价电子对A-B键中结合力贡献的合理性.把这些图与f~i,A-B数据结合起来分析,可和是结论:PDCP比TDCP稳定的主要原因在于前者的几何条件有利于A~1中σ-σ、B~2中σ-pscudo-π和B~1及A~2中π-π共轭效应的发生,使得PDCP中(C(1)-Li键远强于TDCP中的C(1)-Li键.     

STUDY ON CASTOR OIL POLYURETHANE/POLY (METHYL METHACRYLATE) AB CROSSLINKED POLYMERS

Castor oil polyurethane/poly(methyl methacrylate) AB crosslinked polymers (ABCP) were synthesized by free radical copolymerization of MMA and vinyl-terminated castor oil polyurethane which was obtained from isocyanate-terminated castor oil polyurethane and hydroxyethyl methacrylate The mechanical properties, transition and relaxation, as well as compatibility and morphology of the ABCP were investigated by changing the component. The results show that the ABCP is a semicompatible system and the compatibility of the two components decreases with increasing content of the hard segment. The mechanical and damping properties of the ABCP are obviously superior to that of their homopolymers. The damping value is mainly controlled by cross[ink density of the ABCP but the T-g value by component.     

气态肼的三种电子能谱和量子化学研究

本文应用X射线光电子能谱技术测得了气态肼的内层电子能谱、Auger电子能谱和价带电子能谱,对其电子结构进行了系统研究。又采用了不同能量的X射线为激发源,对比了Mg Ka 和 Zr M:价带能谱,定性地获得了肼的分子轨道的组成。本文对肼电子能谱进行了量子化学研究,用从头计算法给出了分子轨道波函数的成分,并指认了能谱,实验结果和计算值之间的一致性很好。