3-氨基-2-吡啶酮互变异构的密度泛函理论计算

采用密度泛函理论,在B3LYP/6-3 l1G**基组水平上,计算并考察了3-氨基-2-吡啶酮分子酮式和烯醇式结构进行结构互变的质子迁移过程中的2种可能途径:(a)分子内质子迁移,(b)水助质子迁移.计算结果表明,途经b所需要的活化能较小,氢键在降低反应活化能方面起着重要作用.     

5-卤代1,2,3,-三唑互变异构的密度泛函理论研究

用密度泛函B3LYP/6-311 G**方法,对气相和水相中的1,2,3三,-唑及5-卤(-F、C l和-B r)代1,2,3,-三唑互变异构体进行了几何构型全自由度优化,获得了它们在气相和水相中的几何结构和电子结构。计算结果显示,在气相和水相中1,2,3三-唑和5-卤代1,2,3三-唑的N2-H型要比对应的N1-H型和N3-H型稳定。讨论了不同的取代基团和溶剂化效应对互变异构体的几何结构、能量和电荷分布以及互变异构反应活化能的影响带。并进一步研究了N1-H、N2-H和N3-H型三唑之间的互变异构机理:(a)分子内质子转移;(b)水助质子转移。计算结果表明,途径(b)所需要的活化能较小,为120.06KJ/mol,途径(a)为204.12KJ/mol。     

W波段回旋行波管放大器速度零散的分析

通过包含速度零散影响的回旋行波管放大器的非线性理论模型,以W波段两段结构回旋行波管放大器为例,详细分析了速度零散对放大器电子注—波互作用的影响.模拟结果表明,通过合理地调整互作用长度,减小电子横纵速度比、调节工作磁场等方法可以有效地减小速度零散的影响,对回旋行波管放大器的优化设计提供了理论依据.     

洁净和氧吸附的Cu(100)表面重构的理论研究

The interaction of atomic oxygen with the clean Cu(100) surface has been studied by means of cluster and periodic slab models density functional theory in the present paper. The Cu(4,9,4) cluster and a three-layer slab with c(2×2) structure are used to model the perfect Cu(100) surface. Three possible adsorption sites,top, bridge and hollow site, were considered in the calculations. The predicted results show that the hollow site is the prefer site for atomic oxygen adsorbed on Cu(100) surface energetically. This is in good agreement with the experiment. The calculated binding energies are respective 2.014, 3.154 and 3.942 eV for top, bridge and hollow sites at mPW1PW91/LanL2dz level for the cluster model. The geometry of Cu(100) surface has also been optimized theoretically with various density functional methods and the results show that the prediction from the B3PW91/LanL2dz and mPW1PW91/LanL2dz reproduce the experimental observation.The frontier molecular orbitals and partial density of states analysis show that the electron transfer from the d orbital of substrate to the p orbital of the surface oxygen atom.     

温度对α-Al2O3(0001)表面吸附生长ZnO影响的DFT研究

The adsorption and the growth of ZnO on α-Al2O3(0001) surface at various temperatures were theoretically calculated by using a plane wave pseudopotentials (USP) method based on density functional theory.The average adsorption energy of ZnO at 400, 600 and 800 ℃ is 4.16±0.08, 4.25±0.11 and 4.05±0.23 eV respectively. Temperature has a remarkable effect on the structure of the surface and the interface of ZnO/α-Al2O3(0001). It is found that the Zn-hexagonal symmetry deflexion does not appear during the adsorption growth of ZnO at 400 ℃, and that the ZnO10-10 is parallel with the 10-10 of the α-Al2O3(0001), which is favorable for forming ZnO film with the Zn-terminated surface. It is observed from simulation that there are two kinds of surface structures in the adsorption of ZnO at 600 ℃: one is the ZnO surface that has the Zn-terminated structure, and whose 10-10 parallels the 10-10 of the substrate surface, and the other is the ZnO10-10 //sapphire 11-10 with the O-terminated surface. The energy barrier of the phase transition between these two different surface structures is about 1.6 eV, and the latter is more stable. Therefore,the suitable temperature for the thin film growth of ZnO on sapphire is about 600 ℃, and it facilitates the formation of wurtzite structure containing Zn-O-Zn-O-Zn-O double-layers as a growth unit-cell. At 600 ℃, the average bond length of Zn-O is 0.190±0.01 nm, and the ELF value indicates that the bond of (substrate)-O-Zn-O has a distinct covalent character, whereas the (Zn)O-Al (substrate) shows a clear character of ionic bond. However, at a temperature of 800 ℃, the dissociation of Al and O atoms on the surface of the α-Al2O3(0001) leads to a disordered surface and interface structure. Thus, the Zn-hexagonal symmetry structure of the ZnO film is not observed under this condition     

吲唑、3-卤代吲唑互变异构反应机理的理论研究

The molecular structures of indazole and 3-halogeno-indazole tautomers were calculated by the B3LYP method at the 6-311G** level, both in the gaseous and aqueous phases, with full geometry optimization.The geometry and electronic structure of the tautomers of indazole, 3-halogeno-indazole and their transition states were obtained. The Onsager solvate theory model was employed for the aqueous solution calculations.The results of the calculation indicated that the N1-H form of the studied molecule is more stable than that of the N2-H form. The influences of the different 3-halogeno and solvent effects on the geometry, energy,charge and activation energy were discussed. The reaction mechanism of the tautomerization of indazole and 3-halogeno-indazole was also studied and a three-membered cyclic transition state of the tautomer reaction has been obtained.     

一种可能的简并谱NNS分布

To expose the statistical properties of the degenerated spectrum, with the aid of the random matrix theory,a possible form of the NNS distribution function of the degenerate spectrum was proposed by providing a solution in terms of the same-degeneracy case. The results indicate that the target spectrum is transformed into two sub-spectra: a random one and a regular one, and that the repulsion level of the regular spectrum is also decreased.     

Si(001)-(2×2×1):H表面O2吸附的密度泛函理论研究

A novel model was developed to theoretically evaluate the O2 adsorption on H-terminated Si(001)-(2*2*1) surface. The periodic boundary condition, the ultrasoft pseudopotentials technique based on density functional theory (DFT) with generalized gradient approximation (GGA) functional were applied in our ab initio calculations. By analyzing bonding energy on site, the favourable adsorption site was determined. The calculations also predicted that the adsorption products should be Si=O and H2O. This theoretical study supported the reaction mechanism provided by Kovalev et al. The results were also a base for further investigation of some more complex systems such as the oxidation on porous silicon surface.     

蒽醌及其羟基衍生物的密度泛函理论研究

运用密度泛函理论, 在B3LYP/6-31G*水平上, 对蒽醌及其羟基取代衍生物进行理论计算. 几何全优化的结果表明, 标题化合物均取平面构型, 分子内氢键对几何构型和电子结构影响很大. 基于简谐振动分析求得IR谱频率和强度, 并作了对称性分类和指认, 计算值与实验值良好相符. 运用含时密度泛函理论方法在相同水平上计算了标题物的电子吸收光谱, 发现蒽醌芳环取代衍生物的最低激发单重态均源自HOMO-LUMO(π→π*)跃迁. 基于振动分析, 由统计热力学求得了标题物的热力学性质.     

丙交酯合成过程的理论及实验研究

采用密度泛函方法研究了丙交酯的合成过程, 优化了合成过程中可能出现的化合物的几何构型, 分析了各化合物的振动频率和偶极矩. 在B3LYP/6-31G*和B3LYP/6-311＋G*水平上进行了各化合物的能量计算, 得到了所设计的各模型反应的焓变和吉布斯自由能变. 结果表明, 所选择的各模型反应为吸热反应且近似可逆, 水的控制对丙交酯的形成很重要. 根据量化计算结果与丙交酯合成实验中不同阶段反应体系红外谱图的变化, 提出了丙交酯合成的可能机理.