排序方式: 共有76条查询结果,搜索用时 31 毫秒
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在B3LYP/6-311++g**、MP2/6-311++g(3df,3pd)及MP2/aug-cc-pvtz水平上分别求得H3SiH…MeHn(Me=Na,Mg,Be;n=1或2)复合物势能面上的3个稳定构型,探讨了以Si-H为电子供体的红移反向氢键相互作用(IHB).经MP2/6-311++g(3df,3pd)水平的计算,在3个复合物中,含基组重叠误差(BSSE)校正的单体间相互作用能分别为-5.98、-8.65和-3.96kJ.mol-1,与MP2/aug-cc-pvtz水平下计算得到的-6.18、-9.12和-4.28kJ·mol-1接近,可见3个反向氢键复合物的相对稳定性顺序为:SiH4...MgH2SiH4...NaHSiH4...BeH2.NBO分析及对相关原子化学位移的计算表明,在复合物中,电子流向总体表现为SiH4→MeHn(n=1或2),且直接参与反向氢键形成的H3的化学位移向低场移动.与传统氢键相比,这里Si1-H3既是氢键供体,又是电子供体,从而形成反向氢键相互作用.另外,采用分子中原子理论(AIM)分别对各复合物中相关键鞍点处的电子密度拓扑性质进行了分析,结果表明3个复合物中均存在以静电性质为主的分子间反向氢键弱相互作用. 相似文献
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The left and right inverse eigenvalue problems of generalized reflexive and anti-reflexive matrices 总被引:1,自引:0,他引:1
Let n×n complex matrices R and S be nontrivial generalized reflection matrices, i.e., R∗=R=R−1≠±In, S∗=S=S−1≠±In. A complex matrix A with order n is said to be a generalized reflexive (or anti-reflexive ) matrix, if RAS=A (or RAS=−A). In this paper, the solvability conditions of the left and right inverse eigenvalue problems for generalized reflexive and anti-reflexive matrices are derived, and the general solutions are also given. In addition, the associated approximation solutions in the solution sets of the above problems are provided. The results in present paper extend some recent conclusions. 相似文献
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用完全活性空间多组态(CASSCF)方法对2-氢吡喃分子光激发开环反应机理进行了研究。利用价键理论(VB)和自然键道分析(NBO)探究了沿能量最低反应途径电子的重新分布情况。计算结果表明从S0-Min p®p*垂直激发到Franck-Condon点后很容易弛豫到S1-Min,经较低的势垒到达圆锥交叉点S1/S0。而S1/S0与S1-Min相比能量低0.63eV。这样体系沿非绝热最低反应途径从激发单重态经交叉点S1/S0很容易得到产物S0-Prod。 相似文献
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通过共价键锚固链转移剂4-氰基-4-二硫代苯甲酰基戊酸琥珀酯于硅片表面,然后采用可逆加成-断裂链转移(RAFT)自由基聚合方法制备了聚甲基丙烯酸甲酯(PMMA)高分子刷. 聚合动力学研究表明,在反应进行2小时后,PMMA的厚度随聚合时间的增大而几乎呈线性增大,具有明显的活性聚合特征. 用椭圆偏光仪、X-光电子能谱(XPS)、原子力显微镜(AFM)及接触角测试对硅片表面的PMMA高分子刷进行了表征. 相似文献
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Ling Ling Lv Yong Cheng Wang Hui Wen Liu Qiang Wang 《Theoretical chemistry accounts》2010,127(5-6):507-517
The activation mechanism of the nitrous oxide (N2O) with the Ta(NH2)3 complex on the singlet and triplet potential energy surfaces has been investigated using the hybrid exchange correlation functional B3LYP. The minimum energy crossing point (MECP) is located by using the methods of Harvey et al. The rate-determining step of the N–O activation reaction is the intersystem crossing from 1 2 to 3 2. The reacting system will change its spin multiplicities from the singlet state to the triplet state near MECP-1, which takes place with a spin crossing barrier of 32.5 kcal mol?1, and then move on the triplet potential energy surface as the reaction proceeds. Analysis of spin–orbit coupling (SOC) using localized orbitals shows that MECP-1 will produce the significant SOC matrix element, the value of SOC is 272.46 cm?1, due to the electron shift between two perpendicular π orbitals with the same rotation direction and the contribution from heavy atom Ta. The rate coefficients are calculated using Non-adiabatic Rice-Ramsperger-Kassel-Marcus (RRKM). Results indicate that the coefficients, k(E), are exceedingly high, k(E) > 1012 s?1, for energies above the intersystem crossing barrier (32.5 kcal mol?1); however, in the lower temperature range of 200–600 K, the intersystem crossing is very slow, k(T) < 10?6 s?1. 相似文献
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The insertion and abstraction reaction mechanisms of singlet and triplet CCl2 with CH3MH (M=O, S) have been studied by using the DFT, NBO and AIM methods. The geometries of reactions, the transition state and
products were completely optimized by B3LYP/6–311G(d, p). All the energy of the species was obtained at the CCSD(T)/6–311G(d,
p) level. The calculated results indicated that the major pathways of the reaction were obtained on the singlet potential
energy surface. The singlet CCl2 can not only trigger the insertion reaction with C-H and M-H in four pathways, by which the products P1 [CH3OCHCl2, reaction I(1)], P3[Cl2HCCH2OH, reaction I(2)], P5[CH3SCHCl2, reaction II(1)] and P7[Cl2HCCH2SH, reaction II(2)] are produced respectively, but also abstract M-H, resulting P4 [CH2O+CH2Cl2, reaction I(3)] and P8[CH2S+CH2Cl2, reaction II(3)]. In addition, the important geometries in domain pathways have been studied by AIM and NBO theories.
Supported by the National Natural Science Foundation of China (Grant No. 20335030) and Foundation of Education Committee of
Gansu Province (Grant No. 0708-11) 相似文献