二苯并噻吩结构和性质的理论研究

为了探究煤中噻吩类有机硫化合物降解规律,采用密度泛函理论来对煤的一种含硫模型化合物进行量子化学方面的计算与研究。采用Materials Studio中的Dmol~3程序分析了与煤有关的含硫模型化合物二苯并噻吩(DBT)的结构和相关性质(键角键长、电荷、振动频率、热力学性质、分子反应活性及稳定性)。计算结果显示处于噻吩环结构中的C—S键键能和C—C键键能相等,噻吩环中的C—S键键能大于非环中的C—S键键能;预测噻吩中C—S键更难断裂;模型化合物中的S原子处HOMO伸展较大,是给电子的位置,S原子易失去电子发生反应。     

半经验分子轨道法优化枞酸结构

运用分子轨道理论中的半经验MINDO／3,MNDO与PM3量子化学计算方法分别对松香中的枞酸分子进行几何结构优化,结果表明,3种方法预测枞酸菲环骨架内的键长、键角、两面角结果与文献值基本一致,而菲环外羧基及异丙基的键长、键角和两面角计算值与文献值有较大偏差,这是由于枞酸分子之间氢键作用以及异丙基热运动比较强烈影响的缘故。在不考虑羧基及异丙基相关的键长、键角和两面角之后,发现PM3方法计算的键长、键角与两面角的结果与文献值比较吻合,计算值与文献值的相关系数R^2分别为0．96432、0．91989和0．99912,而MINDO／3和MNDO的计算值与文献值偏差稍为大些。     

系列含二核钼(钨、铬)簇阴离子化合物的理论研究

在密度泛函B3LYP/SDD水平下,本文对9种[(M2OnS4-n)(i-mnt)2]2-(M=Cr,Mo,W;i-mnt=S2C=C(CN)2-2;n=0,1,2)二核簇阴离子的配合物结构进行了全自由度优化,并计算了键长、键角、自然价键轨道NBO等数据。通过对其几何结构和成键特征的理论分析表明两金属原子之间存在M-M金属键,i-mnt配体中存在离域的π电子。轨道分析表明金属原子存在的空d轨道可以通过接受氧或硫的孤电子对形成超分子化合物。     

二苯二硫醚的结构和性质的理论研究

采用Materials Studio中的Dmol3程序对二苯二硫醚的结构和相关性质(键角键长、Mulliken电荷、振动强度、热力学性质、分子得失电子能力和稳定性)进行了理论性研究。通过Dmol3中的geometry optimization计算出各原子的电荷、振动频率等性质。计算结果明二苯二硫醚分子容易得到电子,并且两个硫原子可能是与其它物质亲电反应的作点。     

环氧丁二酸的结构和性质的理论研究

采用Materials Studio中的Dmol3程序对环氧丁二酸的结构和相关性质(键角键长、Mulliken电荷、振动强度、热力学性质、分子得失电子能力和稳定性)进行了理论性研究。通过Dmol3中的geometry optimization计算出各原子的电荷、振动频率等性质。计算结果明环氧丁二酸分子容易得到电子,并且环氧基上氧原子是与其它物质亲电反应的作点。     

半晶态聚乙烯变形机理的分子动力学模拟

采用相间蒙特卡罗方法,建立半晶态聚乙烯模型。在温度350 K,x、y方向压力为0.1 MPa下进行拉伸,探究聚乙烯的拉伸机理和拉伸过程中微观结构的变化。在拉伸过程中,在弹性变形阶段,键长随着应变的增加而增加,键角和二面角也有少量的增加,且键长率先增长。过了屈服极限后,键长、键角和二面角不再增加,有一定量的减小,然后逐渐趋于稳定。变形区域主要发生在非晶区,拉伸时,分子链会发生取向,随着拉伸的进行,分子链发生滑移,最后会出现空穴现象。     

三聚氰胺分子印迹聚合物的理论研究

三聚氰胺为模板,甲基丙烯酸为功能单体,采用量子化学理论研究了三聚氰胺分子印迹聚合物的形成机理,使用计算机模拟软件计算了三聚氰胺、甲基丙烯酸及三聚氰胺分子印迹聚合物的分子结构、能量及键长键角,并讨论计算结果。结果表明三聚氰胺和甲基丙烯酸之间形成了很强的氢键     

过氧化麦角甾醇分子的密度泛函理论研究

采用密度泛函理论(DFT)方法,在B3LYP/6-311+G(2d,p)水平上对过氧化麦角甾醇进行了计算研究。优化得到了过氧化麦角甾醇分子的结构,给出了分子的键长、键角、二面角等参数,并对其进行了1HNMR光谱、IR光谱、UV-Vis光谱理论模拟和自然电荷分析。自然电荷计算表明,羟基O和H原子很可能是关键的活性中心。理论计算结果与实验值符合的很好。     

几种咔唑衍生物结构及红外光谱的理论分析

本文主要是运用量子中密度泛函方法以及含时密度泛函方法,计算含有取代基H原子以及OH基团的两种咔唑衍生物的几何构型、电子结构、前线分子轨道和电子光谱性质。计算结果表明,当在咔唑环上引入不同的基团,对咔唑衍生物的主要键长、键角影响不大。其次,当基团为OH供电基团时,相对基团H来说,最大吸收波长发生了红移,红移大约20nm左右。基团无论是H还是OH, HOMO的电子云分布影响不大,均均匀分子整个分子上,LUMO的电子云发生了变化。     

1,3,3,5,7,7,——六硝基——1,5——二氮杂环辛烷的晶体与分子结构

关于四氮杂环辛烷类型化合物的结构以及结构和性能的关系研究较多,但是1,3,3,5,7,7,—六硝基—1,5,一二氮杂环辛烷(简称HDC)这类八元二氮杂化合物的结构在文献上还很少见。HDC八元环上有两个对称的N—硝胺和偕二硝基。要研究这类结构,探讨结构和性能间的关系,必须先了解分子构型、构象、堆积情况以及键长和键角等结构参数,为此采用X射线单晶衍射的方法测定了它的分子和晶体结构。     

Introducing DInaMo: A Package for Calculating Protein Circular Dichroism Using Classical Electromagnetic Theory

The dipole interaction model is a classical electromagnetic theory for calculating circular dichroism (CD) resulting from the π-π* transitions of amides. The theoretical model, pioneered by J. Applequist, is assembled into a package, DInaMo, written in Fortran allowing for treatment of proteins. DInaMo reads Protein Data Bank formatted files of structures generated by molecular mechanics or reconstructed secondary structures. Crystal structures cannot be used directly with DInaMo; they either need to be rebuilt with idealized bond angles and lengths, or they need to be energy minimized to adjust bond lengths and bond angles because it is common for crystal structure geometries to have slightly short bond lengths, and DInaMo is sensitive to this. DInaMo reduces all the amide chromophores to points with anisotropic polarizability and all nonchromophoric aliphatic atoms including hydrogens to points with isotropic polarizability; all other atoms are ignored. By determining the interactions among the chromophoric and nonchromophoric parts of the molecule using empirically derived polarizabilities, the rotational and dipole strengths are determined leading to the calculation of CD. Furthermore, ignoring hydrogens bound to methyl groups is initially explored and proves to be a good approximation. Theoretical calculations on 24 proteins agree with experiment showing bands with similar morphology and maxima.     

Preparation of dense La0.67Ca0.33MnO3 ceramics by plasma activated sintering and hot-pressing

Highly dense La_0.67Ca_0.33MnO₃ (LCMO) ceramics were prepared by plasma activated sintering (PAS) and hot-pressing (HP). The comparison of structural, magnetic, and electrical transport properties of the LCMO ceramics after PAS and HP were investigated. XRD and SEM analyses confirmed that both samples exhibited orthorhombic phase with highly dense microstructure. The differences of magnetic and electrical transport properties in PAS and HP LCMO ceramics could be attributed to the different grain sizes, which have an effect on grain boundaries, domain states, Mn–O–Mn bond angles and Mn–O bond lengths. On analyzing the fitting data with several empirical equations, the conduction mechanism of the samples was found to be electron-magnon scattering in the ferromagnetic low-temperature region and variable range hopping (VRH) in the paramagnetic high-temperature region.     

Crystal and Molecular Structure of Pyrylium Salts. VI. Crystal and Molecular structure of 2,6-Diphenyl-4-carboxypyrylium perchlorate and of 5,6,7,8-tetrahydro-8-oxo-2,4-diphenyl-1-benzopyrylium perchlorate. A mutual correlation between structural parameters for symmetrically substituted pyrylium rings

Crystal and molecular structure of 2,6-diphenyl-4-carboxypyrylium and 5,6,7,8-tetrahydro-8-oxo-2,4-diphenyl-1-benzopyrylium perchlorates was solved. Analysis of our data and those retrieved form CSDB shows that for compounds with sp² carbon atoms in C4-C41 bond exists very good relationships between lengths of this bond and bond angles at oxygen and at C4 atoms in the pyrylium ring. Good correlation exists too for two aromaticity indices and these bond lengths indicating mostly resonance effect of the substituent on the geometry of the pyrylium ring.     

Fabrication of superhydrophobic surfaces via poly(methyl methacrylate)-modified anodic aluminum oxide membrane

Superhydrophobic surfaces were prepared by poly(methyl methacrylate) (PMMA) or polystyrene (PS) modification on an optimized anodic aluminum oxide (AAO) honeycomb-like structure surface. The AAO membrane was initially etched in sodium hydroxide solution to get a hierarchical polygon-cavity structure in micro- and nano-scales, and then, it was coated with the polymer solution. The obtained polymer-modified AAO films show superhydrophobicity with water contact angles of larger than 150°. The intrinsic contact angles of the PMMA and PS are 68° and 94°, respectively. The morphology and components of the micro-/nano-structure were characterized by SEM and XPS, respectively, and the mechanism is discussed. This work provides a simple method to obtain superhydrophobic surfaces by common polymers without the need for low surface energy compounds.     

Deformation of interatomic bonds in polymers

Values of the deformation of macromolecules due to distortion of valency angles and bond lengths have been determined from shifts of the intrinsic infra-red (i.r.) vibration frequencies. It has been shown that in a polymer under stress there exists a small number (a few percent) of overstressed macromolecular segments. The overstressed segments appear to start at a certain value of deformation and upon further stressing the polymer their number increases proportionally to the deformation. Values of deformation of overstressed segments have been determined at a stress corresponding to the strength of macromolecules. Deformation of highly oriented specimens before their rupture was shown to occur via distortion of valency angles and bond lengths. An increase in valency angles makes the predominant contribution to the deformation of chains     

The shear strength of composite secondary bonded single-lap joints with different fabrication methods

Abstract

The shear strength of composite secondary bonded single-lap joints was studied in this article. To optimize the adhesive thickness and ensure stable mechanical properties, an improved mold was applied. Based on this mold, a total of 15 specimens (180 samples) were examined and they were fabricated with various overlap lengths, curing pressures, adhesive thicknesses, ply angles, and surface treatment methods. The experimental results indicated that the improved mold not only significantly increased the uniformity of the adhesive thickness but also enhanced the shear strength of the joints and the shear strength was improved by approximately 13% compared to that of conventional methods. Moreover, the shear strength was decreased in specimens with increased overlap lengths and increased in samples with an increased curing pressure. Furthermore, the shear strength of the specimens was also affected by the adhesive thicknesses, ply angles, and surface treatment methods. The mechanisms can be ascribed to the effect of the fabrication method on the failure mode. A facile platform for optimizing these parameters is provided in this article. Based on this platform, the shear strength of the joints was enhanced to 33.5?MPa.     

Coronanden mit 1,2-Dithio-ethen-Einheiten. II. Kristallstrukturen der beiden Thiakronenether 8,9-Dicyan-8,9-didehydro-7,10-dithia[12]krone-4 und 11,12-Dicyan-11,12-didehydro-10,13-dithia[15]krone-5

Coronands with 1,2-Dithio-ethene Units. II. Crystal Structures of the Two Crown Thioethers 8,9-Dicyano-8,9-didehydro-7,10-dithia-[12]crown-4 and 11,12-Dicyano-11,12-didehydro-10,13-dithia[15]crown-5 The structures of the title compounds have been determined by X-ray analysis. Both thioethers crystallize in the monoclinic system with the following crystal data. Dithia-[12]crown-4: a = 751.7(1), b = 1010.4(1), c = 1639.8(2) pm, β = 95.08(1)°, Z = 4, space group P2₁/n; dithia[12]crown-5: a = 1169.9(3), b = 916.7(3), c = 1414.1(4)pm, β = 92.51(2)°, Z = 4, space group P2₁/c. The structures were refined to final R = 0.048 (R_w = 0.031) and 0.040 (0.046), respectively. They are characterized by their structural parameters (bond lengths and angles, torsion angles, l.s. planes) and discussed in special consideration of the ring conformation and the geometric arrangement of the donor atoms.     

预膜气流式雾化器的结构尺寸对雾化结果的影响

本文研究了预膜气流式雾化器的结构参数对雾化性能的影响,采用４种具有不同气液冲击角的二流式嘴,改变液体预膜通道 尺寸,以寻求在较小的能耗下,获得良好雾化效果的喷嘴设计参数。     

DENSITY FUNCTIONAL THEORETICAL STUDY OF MONO-NITRATED FLUORANTHENES

The molecules 1-, 2-, 3-, 7-, and 8-nitrofluoranthenes are well-known mutagens and carcinogens. These environmental pollutants are emitted into the atmosphere via anthropogenic activities including diesel combustion emissions, residential home heating and reactions of nitrogen oxide (NO _x ) gases with fluoranthene. The differential mutagenic potency between nitrated fluoranthenes has been proposed to emanate from the orientation of the nitro group relative to the aromatic plane. To establish the validity of the structure-function correlations requires specific crystal structures, which are unavailable. Fortunately, electronic structure calculations can be done. In this report, the structures of fluoranthene and its mono nitrated derivatives were investigated with the density functional theoretical theory at B3LYP/6-311+G?? level. The structure-function correlations were examined by comparing reported mutagenicity data with calculated bond lengths, angles and dihedral angles. The relationships between the calculated structures and the reported mutagenicity in the chemical literature are discussed.