将“节面数”引入HMO法对环共轭体系π分子轨道的求解

休克尔分子轨道法(HMO)是基于建立共轭分子体系的休克尔行列式或久期方程求解得到该分子体系的分子轨道能量Ei及分子轨道波函数ψ_i的表达式。用该方法对环共轭分子体系讨论时,由于环共轭分子具有特殊的首尾相连环状分子结构,求解其久期方程还需引入较为抽象的假定条件。本文将分子轨道波函数中的“节面数”引入对环共轭分子体系讨论,在分子轨道波函数图中直接标示出节面位置,则求解需引入的相关条件可从图中明显得出,使求解过程直观易懂。

CBS方法对单杂环体系C—H键解离焓的实验值评估

用高精度计算方法 CBS-4M,CBS-Q和CBS-QB3评估了26种单杂环分子的C-H键解离焓的实验值.结果表明,CBS-QB3方法最好,MD、MAD及RMSE分别为9.3、9.3和11.1 k J/mol.理论值与实验值的线性相关方程为y=0.928x+21.3,相关系数平方R2达0.980.通过自然键轨道分析后发现,杂原子的电负性使得五元杂环的自然电荷分布发生变化.

以气相氢原子活化金刚石附氢(111)面的分子轨道方法研究

在低压化学气相沉积条件下,金刚石附氢表面脱氢势垒的大小是金刚石薄膜生长动力学的重要理论参数,前人用不同方法对该势垒值的计算给出了很不一致的理论结果。本文应用多种分子轨道方法对金刚石附氢(111)面的脱氢势垒进行了系统研究,比较了各方法计算的过渡态结构,给出了经修正的理论预言值,并论证了不同分子轨道方法计算结果的优劣,评价了前人不相一致的理论结果。

臭氧分子的离域 π键与分子性质

用休克尔分子轨道法从本质上说明了臭氧分子的磁性和极性。

Study on the Phosphenium Cation (Ⅰ)——Synthesis and Characterization of 5-Methylthio-3-N-Phenyl-2,3-2(H)-1,3,4,2-Thiadiazaphosphenium Cation and the Others

Ten years after the first synthesis of neutral two-coordinated phosphorus in 1962, the first phosphenium cations were synthesized by Fleming, Lupton and Jekot in 1972. Up to now, though 30 years have passed, the members of these phosphenium cations are still very few. the research of phosphenium cations is only limited in France, America and other countries. In our laboratory work was done on a new unique cation: the 5-methylthio-3-N-phenyl-2,3-2（H）-1,3,4,2-thiadiazaphosphenium cation which was found and characterized by 261.9 ppm conclusively of 31p NMR. It also has an electric conductivity in nucleophilic and electrophilic reactions. We are interested in noticing that these phospbenium cations are stabilized by one sulfur atom besides nitrogen atoms.