氮杂苯并噁唑分子设计及其电子结构研究

苯并噁唑是一类具有特殊光物理性质的分子,广泛用于有机激光染料。为寻找新的有效分子,在该类分子的实验和理论研究基础上,我们进行了一系列苯并噁唑类分子设计,并用ＰＰＰ方法对所设计的分子的电子结构等特性进行了较详细的研讨,从中选出了一些具有特殊性的 分子,这些分子有可能成为更优良的新型材料。     

Effects of Solvent Molecules on the Interlayer Spacing of Graphene Oxide

Graphene oxide(GO) contains numerous functional groups that facilitate the intercalation of polar solvents. The properties and applications of GO are closely related to its interlayer spacing. We report on the changes in the interlayer spacing of GO after the adsorption of water molecules and the polar organic solvents C_2H_6O_2(EG), C_3H_7NO(DMF), C_5H_9NO(NMP). Experiments were conducted to investigate the variations in the functional groups and structure of GO after solvent adsorption, and they play a vital role in modeling and verifying the results of molecular dynamics simulation. The most stable GO structures are obtained through molecular dynamics simulation. The expansion of the interlayer spacing of GO after the adsorption of monolayer solvent molecules corresponds to the minimum three-dimensional size of the solvent molecules. The spatial arrangement of solvent molecules also contributes to the changes in interlayer spacing. Most adsorbed molecules are oriented parallel to the carbon plane of GO. However, as additional molecules are adsorbed into the interlaminations of GO, the adsorbed molecules are oriented perpendicular to the carbon plane of GO, and a large space forms between two GO interlayers. In addition, the role of large molecules in increasing interlayer spacing becomes more crucial than that of water molecules in the adsorption of binary solvent systems by GO.     

B2H6分子声子态及声子间耦合的群论分析与Mathematica应用

利用群论和对称性分析的方法研究了具有D3d对称性构型的B2H6分子的声子态及其声子间耦合等问题。研究发现,B2H6存在5种不同的声子态,它们分别具有D3d群下的a1g、a1u、a2u、eg与eu对称性,其中a2u与eu具有红外活性,a1g和eg具有拉曼活性,而a1u是非活性的;在B2H6的声子态中只有eg是活跃的声子态;活跃声子态eg与eg之间的耦合作用将会产生耦合声子态a1g和eg;B2H6分子的电声耦合作用一定会导致B2H6分子发生杨-泰勒畸变,畸变致使B2H6分子从D3d对称性降低到C2h对称性。     

B2H6分子声子态及声子间耦合的群论分析与Mathematica应用

利用群论和对称性分析的方法研究了具有D3d对称性构型的B2H6分子的声子态及其声子间耦合等问题。研究发现,B2H6存在5种不同的声子态,它们分别具有D3d群下的a1g、a1u、a2u、eg与eu对称性,其中a2u与eu具有红外活性,a1g和eg具有拉曼活性,而a1u是非活性的;在B2H6的声子态中只有eg是活跃的声子态;活跃声子态eg与eg之间的耦合作用将会产生耦合声子态a1g和eg;B2H6分子的电声耦合作用一定会导致B2H6分子发生杨-泰勒畸变,畸变致使B2H6分子从D3d对称性降低到C2h对称性。     

Investigation of structures similarity of organic substances

According to similarity property principle, structurally similar molecules tend to have similar properties. Similar molecules exhibit similar biological activities. However, there is no hard and fast rule that the compounds with similar chemical structure will have similar functions. There are several compounds of similar chemical structure with significantly different biological actions and activities. Structure similarity of natural products can be investigated using Tanimoto coefficient and Euclidean distance measurements. To do this, the molecules are decomposed into smaller fragments, and a dictionary, of the fragments are prepared. Using the dictionary, 2D fingerprints are formed. With the fingerprints Tanimoto coefficient and Euclidean distance are quantitated.     

等电子原理与小分子结构规则

用等电子原理对非过渡系ＡＢｎ型分子或离子的结构特点进行归纳,可以得到一些重要的分子结构规则．这些结构规则以总配位数式和等电子分子周期表为其集中的体现形式．     

群论框架下具有D3d对称性构型的B2H6分子的声子间耦合及其杨-泰勒畸变

依据群论与量子理论,利用对称性分析的方法探讨了具有D3d对称性构型的BzH6分子的声子间耦合及其杨一泰勒畸变．研究了B2H6分子的电子态与声子态的对称性以及其活跃的声子态,导出了B2H6分子的eg声子间耦合的CG系数计算公式,在此基础上进一步计算出了这些CG系数值．接着又分析了B2H6分子的杨一泰勒畸变方向及其基态能级的分裂,发现B2H6分子的杨一泰勒畸变方向是D3d→C2h畸变导致B2H6分子的二重简并的能级发生分裂,因此其能级的简并性因畸变而被完全消除．     

利用一种新的势能函数精确计算双原子的光谱参数

A novel scheme for potential energy functions of diatomic molecules is derived using a function with phase factors. Six kinds of potential curves of common shapes are obtained by adjusting the phase factors. Spectroscopic parameters of the ground states for ten kinds of molecules are calculated using the potential energy functions. The results agree well with experimental data.     

Common Molecules: Bringing Research and Teaching Together Through an Online Collection

The World Wide Web contains a number of collections of data files for molecules with limited usability and utility for users. We describe the design of a Common Molecules collection that provides interactive tools for 3-D visualization of molecules. Our organizational design is intuitive and our collection is large, growing, and provides not only structural information, but also historical and/or key information on the properties of the molecules in the collection. The use of the collection by students and the role of students in the development of the collection are also described.     

严格计算输运过程的2问题

本文利用参与定向运动动量输运的分子数是总分子数的16的假设,综合通过考虑分子的速度分布及分子从各个方向穿过dA面,阐述了一种既严格又简明计算输运过程无碰撞地穿过dA面的分子之平均自由程方法。     

金属表面单原子操纵研究进展

扫描隧道显微镜或原子力显微镜使人们能够操纵吸附在材料表面的单个原子或分子．这种技术可从单个原子、分子开始组装具有特定功能的纳米结构,也能组装、拆解分子从而控制化学反应的进程,将在物理、化学等多学科领域发挥重要作用．本文综述了近年来在金属材料表面进行单原子操纵的研究进展,介绍了单原子操纵的方法和机制,并对有待进一步研究的若干问题进行初步探讨．     

蛋白质晶体生长方法综述

蛋白质晶体的生长过程是蛋白质分子与周围环境相互作用的结果.蛋白质晶体的生长分为成核、生长和停止三个阶段.对蛋白质的结晶条件进行筛选、种晶可获得晶核.通过改变蛋白质本身来获得单晶的方法有：截短、修饰、共晶和寻找同源蛋白质.蛋白质的结晶条件仍有待于进一步深入研究.     

严格计算输运过程的2(λ-)问题

本文利用参与定向运动动量输运的分子数是总分子数的1/6的假设,综合通过考虑分子的速度分布及分子从各个方向穿过dA面,阐述了一种既严格又简明计算输运过程无碰撞地穿过dA面的分子之平均自由程方法.     

X-ray Crystallography of biological macromolecules

The three-dimensional structures of thousands of biological macromolecules have been determined by X-ray diffraction, since the first structures were reported about half a century ago. The structures revealed how critical the shapes and sizes of the molecules are to perform various biological processes in living creatures. In addition to providing atomic details of how the molecules function and interact with other molecules, the structures help in designing medicines. K Suguna is at the Molecular Biophysics Unit Indian Institute of Science Bangalore. Her research involves the determination of the crystal structures of macromolecules by the X-ray diffraction method. She is interested in the structures and functions of biological macromolecules.     

Molecule Matters van der Waals Molecules

In Part 2 of this series, we discuss homo- and hetero-nuclear noble gas dimers. Experimental and theoretical results for dimers containing He, Ne, Ar, Kr and Xe are reviewed. These dimers are bound by London dispersive forces, which is one component of the van der Waals or intermolecular forces. Though these are usually called van der Waals complexes or van der Waals molecules, these dimers may be more appropriately called London molecules. Heliumdimer is a particularly interesting case with the equilibrium internuclear distance estimated to be about 50 Angstrom.     

双原子分子的键长与原子结构之间定量关系的研究

根据原子结构的特点,探讨了双原子分子的键长与组成双原子分子的原子结构之间的关系,发现双原子分子的键长与组成双原子分子的原子结构之间存在着良好的定量关系,据此提出一种直接根据原子结构预测双原子分子键长的方法．结构表明,预测值与实验值的一致性令人满意,平均误差0．0058nm．     

Molecules to materials

Earlier articles in this series provided several examples to illustrate the controlled assembly of bulk structures with desired solid state properties using specifically designed molecules. The ultimate goal of these exercises is the development of devices whose building blocks are molecules. This article and the next attempt to impart the flavour of this exciting field of research and technology through brief discussions of several molecular devices. This article will focus on devices, which utilise the bulk properties of molecular materials; the examples selected are electroluminiscent device, thin film transistor and an electro-optic device.     

关于集合概念与非集合概念

逻辑学的基础是事物的＂类＂。而事物的＂类＂是由相同的个别事物即＂分子＂构成的。结合逻辑思维的实际情况,有必要把＂分子＂分为集合体和非集合体两种情况,而集合概念与非集合概念的区分,正是由于它们所反映的分子情形不同。正确地区分集合概念与非集合概念,对于解决逻辑学中仍然存在的一些理论问题和人们日常思维中遇到的实际问题,都有很大的帮助。     

在电化学体系下邻硝基苯甲酸的表面增强拉曼光谱

在电化学体系下,让微溶于水的临硝基苯甲酸分子吸附在粗糙的Ag电极上,使用波长为514.5nm的激光激发,得到了非常精细的表面增强拉曼光谱。改变电极上的电位,所得表面增强拉曼光谱峰和强度也是发生变化,进一步的推断临硝基苯甲酸分子在Ag纳米颗粒上吸附方式。     

浅析混合气体温度的分子动力学

一般认为质量相同、温度不同的同种气体有相同的分子数,则它们混合后,达到热平衡的温度为原来温度之和的一半.然而,根据狭义相对论,可以得出质量相同、温度不同的同种气体含有不同数目的分子,进而可以推出对于质量相同、温度分别为T1、T2的同种气体混合后,达到热平衡的温度不等于T1与T2之和的一半.