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1.
采用Gaussian-03程序中的MP2/6-311++G(2d,2p)方法,优化了FH- Rg(Rg=He,Ne,Ar)二聚体的结构.使用MELD精密从头计算中的CISD方法,结合我们自编的程序,计算了这些二聚体的单电子作用势(PAEM),并绘出了它们的分子形貌图象.分子形貌所提供的形貌特征、前沿电子密度的特征等,可以直观地揭示He,Ne和Ar等原子与HF分子相互作用时2种相互作用的差别,即共价相互作用与非共价相互作用区分的直观形象的表征.从二聚体的内禀特征信息可以看出,F,H和Rg原子都发生了不同程度的变形,HF分子对惰性气体原子有一定影响,而惰性气体原子对HF分子的影响较小.  相似文献   

2.
利用Hartree-Fock 方法在6-31G*水平上对聚苯分子进行了计算研究. 分别从几何构型、分子轨道空间分布和分子轨道能级三个方面讨论了外电场对寡聚苯分子导线的影响, 给出了分子导线的性质与外电场的关系. 进一步, 连接硫原子于聚苯分子的两端, 并共价结合在金电极上. 利用非平衡格林函数方法对其在0-2.0 V 偏压下电子输运特征进行了深入研究.  相似文献   

3.
关于分子特征形状的理论   总被引:3,自引:0,他引:3       下载免费PDF全文
借助于分子中电子运动的经典转折点, 定义了分子的内禀特征轮廓. 文中以甲烷、甲醇和甲酸为例, 详细介绍了分子内禀特征轮廓理论方法. 对分子轮廓的特征截面的具体分析, 可以给出形成分子过程中原子的空间变化信息. 首次计算和绘出了上述分子轮廓上的电子密度分布图, 它与分子的化学性质密切相关, 给出了对分子边界的新认识.  相似文献   

4.
运用量子化学密度泛函B3LYP方法, 采用6-311++G(d,p)及aug-cc-pVDZ基组, 通过CP校正的几何梯度优化对(CH2)2O和(CH2)2S与双卤分子XY (XY=Cl2, Br2, ClF, BrF, BrCl)形成的卤键复合物的几何构型、振动频率和相互作用能等进行了研究. 利用电子密度拓扑分析理论方法对卤键复合物的拓扑性质进行了分析研究, 探讨了该类分子间卤键的作用本质. 结果表明, (CH2)2O和(CH2)2S与双卤分子间的卤键介于共价键与离子键之间, 偏于静电作用成分为主. 形成卤键后, 双卤分子的键长增加, 振动频率减小, 原子积分性质发生改变. 卤键键长的变化、键能的强弱、键鞍点处的电子密度值与双卤分子的电负性有关.  相似文献   

5.
Rg-HX分子间势的精确从头计算研究   总被引:3,自引:0,他引:3  
张愚  史鸿运  王伟周 《物理化学学报》2001,17(11):1013-1020
在用非迭代的三重激发项来校正CCSD的CCSD(T)理论水平下,采用aug cc pVQZ基函数对He HF的分子间势进行了系统的研究.结果表明:He HF以线型结构存在.在极限基的情况下,复合物两种线型极小点结构He H F和He F H势阱深分别为46.614 cm-1和25.026 cm-1,对应He原子到HF分子质心的距离Rm分别为0.3149 nm和0.3012 nm.讨论了不同的基函数和理论方法在研究此类弱束缚态复合物的分子间势时的可靠性及其对结果的影响,并研究了HF分子中H-F键长的改变对势能的影响,同时也给出了势函数的解析形式.  相似文献   

6.
应用分子形貌理论, 研究了类SN2反应过程中的沿着IRC路径上固定点的分子形貌的特征, 计算给出了形状和电子密度特征参数以及各键的Dpb值. 应用Matlab程序绘制了分子特征边界轮廓上的电子密度分布的三维图像, 即分子形貌像, 给出了这类反应的动态变化过程.  相似文献   

7.
借助于分子中电子运动的经典转折点,定义了分子的内禀特征轮廓.文中以甲烷、甲醇和甲酸为例,详细介绍了分子内禀特征轮廓理论方法.对分子轮廓的特征截面的具体分析,可以给出形成分子过程中原子的空间变化信息.首次计算和绘出了上述分子轮廓上的电子密度分布图,它与分子的化学性质密切相关,给出了对分子边界的新认识.  相似文献   

8.
倪杰  黎安勇  闫秀花 《物理化学学报》2008,24(11):2000-2006
运用量子化学从头算方法研究了HNO与分子簇(HF)1≤n≤移氢键, 重极化与重杂化和分子内超共轭导致了氢键的蓝移; 所有的X…H—F(X=O, N, F)氢键都是红移的, 分子间超共轭导致了氢键的红移. 在多分子体系形成的氢键链中, 分子间超共轭作用呈现规律性递变, 它导致了氢键强度与频率位移的规律性变化, 电子密度拓扑分析结果反映和支持了这种规律性变化.  相似文献   

9.
运用量子化学从头算方法研究了HNO与分子簇(HF)1≤n≤3形成的蓝移与红移氢键.在这些体系中,F…H-N都是蓝移氢键,重极化与重杂化和分子内超共轭导敛了氰键的蓝移;所有的X…H-F(X=O,N,F)氢键都是红移的,分子问超共轭导致了氢键的红移.在多分子体系形成的氢键链中,分子问超共轭作用呈现规律性递变,它导致了氢键强度与频率位移的规律性变化,电子密度拓扑分析结果反映和支持了这种规律性变化.  相似文献   

10.
《化学通报》2001,64(9):579-582
用自洽场理论(HF)和密度泛函理论(DFT)的B3LYP方法,在6-31G*的水平上对化合物(HAlNH)2和(HAlNH)3的几何结构进行优化,并分别与环丁二烯C4H4和苯分子C6H6的结构和成键方式进行比较.以B3LYP/STO-3G方法讨论其分子轨道波函数(ψ).结果表明C4H4和(HAlNH)2均为D2h对称,前者为长方形结构,形成两个孤立的π键;而后者为菱形结构,形成一个π44键.C6H6和(HAlNH)3分子点群分别为D6h和D3h,并均形成一个π66键.成键原子对分子轨道的贡献不同,其中C原子是完全等价的,而Al和N原子各不相同,N原子比Al的贡献要大得多.  相似文献   

11.
12.
Understanding the effects of intermolecular interactions on the charge-transport properties of metal/molecule/metal junctions is an important step towards using individual molecules as building blocks for electronic devices. This work reports a systematic electron-transport investigation on a series of "core-shell"-structured oligo(phenylene ethynylene) (Gn-OPE) molecular wires. By using dendrimers of different generations as insulating "shells", the intermolecular π-π interactions between the OPE "cores" can be precisely controlled in single-component monolayers. Three techniques are used to evaluate the electron-transport properties of the Au/Gn-OPE/Au molecular junctions, including crossed-wire junction, scanning tunneling spectroscopy (STS), and scanning tunneling microscope (STM) break-junction techniques. The STM break-junction measurement reveals that the electron-transport pathways are strongly affected by the size of the side groups. When the side groups are small, electron transport could occur through three pathways, including through single-molecule junctions, double-molecule junctions, and molecular bridges between adjacent molecules formed by aromatic π-π coupling. The dendrimer shells effectively prohibit the π-π coupling effect, but at the same time, very large dendrimer side groups may hinder the formation of Au-S bonds. A first-generation dendrimer acts as an optimal shell that only allows electron transport through the single-molecule junction pathway, and forbids the other undesired pathways. It is demonstrated that the dendrimer-based core-shell strategy allows the single-molecule conductance to be probed in a homogenous monolayer without the influence of intermolecular π-π interactions.  相似文献   

13.
In molecular electronics, the conductance strongly depends on the frontier energy levels and spatial orientations of molecules. Utilizing these features, we investigate the electron transport characteristics of conjugated molecules attached on an armchair graphene nanoribbon. The resulting sharp reduction in the transmission which represents molecular fingerprints and the change of the transmission depending on the molecular orientation, are examined in accordance with a unified picture of the Fano–Anderson model. These characteristics, being unique for each molecule, would be applicable to molecular recognition and configurational analysis. © 2014 Wiley Periodicals, Inc.  相似文献   

14.
基于密度泛函理论研究了非对称双笼型单分子溶剂化电子e-@C24F22(NH)2C20F18(1、2 和3), 进一步展示了我们提出的一种新型电子异构体——(非对称型的)笼间电子迁移异构体. 1、2 和3 具有显著不同的偶极矩. 由于都存在两个氧化还原中心, 它们属于一种非金属型的新型Robin-Day II-III 分子. 对于1 和3, 额外电子分别定域在C24F22和C20F18笼里(Robin-Day II); 对于2, 额外电子则离域于两个非对称的笼中(Robin-Day III). 值得注意的是, 在y 轴方向上外加-0.0004和-0.0008 a.u.的临界电场(Ec)时可分别使1 的额外电子从C24F22笼中部分和全部地迁移到C20F18笼中, 即实现从1 到2 再到3 的转化; 当Ec为0.0004 a.u.时, 3 的额外电子从C20F18笼中全部迁移到了C24F22笼中, 即3 未经过2 直接转化成了1.  相似文献   

15.
16.
Understanding electron transport through a single molecule bridging between metal electrodes is a central issue in the field of molecular electronics. This review covers the fabrication and electron‐transport properties of single π‐conjugated molecule junctions, which include benzene, fullerene, and π‐stacked molecules. The metal/molecule interface plays a decisive role in determining the stability and conductivity of single‐molecule junctions. The effect of the metal–molecule contact on the conductance of the single π‐conjugated molecule junction is reviewed. The characterization of the single benzene molecule junction is also discussed using inelastic electron tunneling spectroscopy and shot noise. Finally, electron transport through the π‐stacked system using π‐stacked aromatic molecules enclosed within self‐assembled coordination cages is reviewed. The electron transport in the π‐stacked systems is found to be efficient at the single‐molecule level, thus providing insight into the design of conductive materials.  相似文献   

17.
18.
Based on the molecular face (MF) theory, the molecular face surface area (MFSA) and molecular face volume (MFV) are defined. For a variety of organic molecules and several inorganic molecules, the MFSA and MFV have been studied and calculated in terms of an algorithm of our own via the Matlab package. The MFV shows a very good linear relationship with the experimentally measured critical molar volume. It is also found that the MFSA and MFV have significant linear correlations with those of the commonly used hard‐sphere model and the electron density isosurface. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010  相似文献   

19.
In this work we investigate a new fluorescent molecular switch based on the interconversion between the fluorescent zwitterionic form (ZW1) and the non-fluorescent anionic state (MC2) of a spirocyclic Meisenheimer complex of 1,3,5-trinitrobenzene. Density functional theory molecular orbital calculations reveal that photo-induced electron transfer from a guanidine group to the trinitrocyclohexadiene fluorophore of the complex quenches the emission from MC2. Protonation, as well as coordination of other Lewis acids to the guanidine group, suppress the quenching mechanism and allow the complex to fluoresce. In agreement with the calculations, reversible on-off fluorescence switching of the ZW1-MC2 bulk system occurs by protonation-deprotonation of the guanidine moiety upon acid-base addition. Interestingly, spectroelectrochemical ensemble measurements show that switching of the ZW1-MC2 pair can also be attained electrochemically, thus unraveling the versatile functioning of this system. The ultimate limit of monitoring the reversible on-off operation of individual switch molecules is reached by means of single-molecule fluorescence spectroscopy, which demonstrates the potential of the ZW1-MC2 system to be used as a true single-molecule switch on the nanometer scale.  相似文献   

20.
In recent years, a number of approaches have emerged that enable far‐field fluorescence imaging beyond the diffraction limit of light, namely super‐resolution microscopy. These techniques are beginning to profoundly alter our abilities to look at biological structures and dynamics and are bound to spread into conventional biological laboratories. Nowadays these approaches can be divided into two categories, one based on targeted switching and readout, and the other based on stochastic switching and readout of the fluorescence information. The main prerequisite for a successful implementation of both categories is the ability to prepare the fluorescent emitters in two distinct states, a bright and a dark state. Herein, we provide an overview of recent developments in super‐resolution microscopy techniques and outline the special requirements for the fluorescent probes used. In combination with the advances in understanding the photophysics and photochemistry of single fluorophores, we demonstrate how essentially any single‐molecule compatible fluorophore can be used for super‐resolution microscopy. We present examples for super‐resolution microscopy with standard organic fluorophores, discuss factors that influence resolution and present approaches for calibration samples for super‐resolution microscopes including AFM‐based single‐molecule assembly and DNA origami.  相似文献   

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