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排序方式: 共有179条查询结果,搜索用时 15 毫秒
71.
用相对论赝势的从头算法研究了铀酰离子的几何构型和电子结构.得到了与实验数据较一致的键长、键角和IR振动频率.铀氧间以U5f与O2p相互作用为主,U6d与O2p间的键合较小;同时,U6p、U7s、U6d和Usd杂化轨道与O2s间也有强的相互作用.不同自旋多重度时对铀酰离子总能量计算结果表明,UO22+的基态为1∑g+的可能性更大. 相似文献
72.
Density functional theory B3LYP method with 6‐31G* basis set has been used to optimize the geometries of the catechin, water and catechin‐(H2O)n complexes. The vibrational frequencies have been studied at the same level to analyze these complexes. Six and eleven stable structures for the catechin‐H2O and catechin‐(H2O)2 have been found, respectively. Theories of atoms in molecules (AIM) and natural bond orbital (NBO) have been utilized to investigate the hydrogen bonds involved in all the systems. The interaction energies of all the complexes corrected by basis set superposition error, are from ?13.27 to ?83.56 kJ/mol. All calculations also indicate that there are strong hydrogen‐bonding interactions in catechin‐water complexes. The strong hydrogen‐bonding contributes to the interaction energies dominantly. The O–H stretching motions in all the complexes are red‐shifted relative to that of the monomer. 相似文献
73.
Yi Meng Yi Luo Ji‐Long Shi Huimin Ding Xianjun Lang Wei Chen Anmin Zheng Junliang Sun Cheng Wang 《Angewandte Chemie (International ed. in English)》2020,59(9):3624-3629
The construction of 2D and 3D covalent organic frameworks (COFs) from functional moieties for desired properties has gained much attention. However, the influence of COFs dimensionality on their functionalities, which can further assist in COF design, has never been explored. Now, by selecting designed precursors and topology diagrams, 2D and 3D porphyrinic COFs (2D‐PdPor‐COF and 3D‐PdPor‐COF) are synthesized. By model building and Rietveld refinement of powder X‐ray diffraction, 2D‐PdPor‐COF crystallizes as 2D sheets while 3D‐PdPor‐COF adopts a five‐fold interpenetrated pts topology. Interestingly, compared with 2D‐PdPor‐COF, 3D‐PdPor‐COF showed interesting properties, including 1) higher CO2 adsorption capacity; 2) better photocatalytic performance; and 3) size‐selective photocatalysis. Based on this study, we believe that with the incorporation of functional moieties, the dimensionality of COFs can definitely influence their functionalities. 相似文献
74.
An ab initio study of the possible interaction between several anions (F(-), Cl(-), N(3)(-), N(4)(-), and N(5)(-)) and tri-s-triazine molecule, an electron-deficient aromatic ring, has been carried out at the B3LYP and MP2 levels of theory. Minima are located corresponding to hydrogen bonding, pi-pi stacking, and reactive complexes. This novel mode of bonding suggests the development of new cyclophane-type receptors for the recognition of anions. 相似文献
75.
LC4—M材料复合型韧断主要影响因素的分析 总被引:5,自引:0,他引:5
通过分析LC4-M铝合金材料在不同复合比载荷下的断裂试验结果,参照常规断裂现象,修正了一般断裂试验中认定裂纹启裂方向的方法,结合不同复合比下裂尖附近应力三维、主应力方向的计算分析,得到:在裂端的钝化变形区域、应力三维度的极大值处,对应于裂纹的启裂位置,即使在高韧性材料中发生剪切断裂的情况下也是如此;裂纹的启裂方向在拉伸断裂时与启裂点最大拉应力方向有关,在剪切断裂时启裂点最大剪应力方向有关,引起两种形式断裂的主要因数和破坏机理有很大不同。 相似文献
76.
在RHF/6-31G^**,MP2/6-31G^**,B3LYP/6-31G^**水平下优化了5,6,9,10-四脱氢苯并环辛烯的平衡几何构型。用B3LYP/6-31G^**方法计算了该化合物的红外光谱、拉曼光谱、核磁共振谱。计算结果与实验结果吻合很好,从而在理论上证实了它的存在。用等键反应分析,自然键轨道方法对它的稳定性和共轭性分别进行了讨论。结果表明5,6,9,10-四脱氢苯并环辛烯分子平面刚性结构,可能稳定存在,但由于苯环共轭性的削弱和较高的张力,使得它易于分解。 相似文献
77.
Jin Guo Tingfeng Wang Dinan Wang Junfeng Shao Anmin Chen Mingxing Jin 《Applied Physics A: Materials Science & Processing》2014,117(3):1367-1374
The thermionic emission of the single-layer gold thin film and the two-layer film was assembled by gold padded with other metals (Ag, Cu, and Ni) and irradiated by the femtosecond laser pulse. Additionally, the emission was simulated by a two-temperature model combined with the Richardson–Dushman equation. It was found that the two-layer metal structure can change the electron temperature of the gold surface and control the thermionic emission compared with the single-layer gold film. With the same laser fluence, the two-layer film structure may shorten the duration of thermionic emission, and the duration of the thermionic emission can be further optimized by changing the proportion of thin film thickness with gold layer in the two-layer structure. The result can be especially beneficial in the context of ultrafast electron emission induced by femtosecond laser. 相似文献
78.
S~6中具有常数Kahler角的极小曲面 总被引:4,自引:0,他引:4
球面S6具有典型的近复结构,因而对于其中的曲面可引入Kahler角的概念.本文研究S6内具有常数Kahler角的极小曲面,得到了刚性定理.结合已有结果,易知Simon猜想对于这类曲面成立. 相似文献
79.
80.
The C-Hal (Hal = Cl, Br, or I) bond-length change and the corresponding vibrational frequency shift of the C-Hal stretch upon the C-Hal···Y (Y is the electron donor) halogen bond formation have been determined by using density functional theory computations. Plots of the C-Hal bond-length change versus the corresponding vibrational frequency shift of the C-Hal stretch all give straight lines. The coefficients of determination range from 0.94366 to 0.99219, showing that the correlation between the C-Hal bond-length change and the corresponding frequency shift is very good in the halogen-bonded complexes. The possible effects of vibrational coupling, computational method, and anharmonicity on the bond-length change-frequency shift correlation are discussed in detail. 相似文献