一类新型含平面四配位碳、硅和锗的化合物的结构与成键性质

采用密度泛函理论方法,研究了一类新型含平面四配位碳、硅和锗的化合物的结构、成键、稳定性和光谱性质.通过结构优化和振动分析表明,这类含有平面四配位结构单元CB4、SiN4、GeN4、GeB4的分子具有稳定的电子和几何结构.这些稳定体系均存在中心原子与周围4个原子间的共轭π键,其中中心原子C为π电子给体,Si为π电子受体,...     

靛蓝与异构体靛玉红的量子化学研究

靛蓝与靛玉红是青黛的主要成分，也是同分异构体，但是它们的理化性质和生物活性却显示出明显的差异，作者选用B3LYP的方法，基组为6-31G，优化了这两种同分异构体的几何构型，得到了两者之间的异构化能，进行了集居数分析、自然键轨道(NBO)分析、成键轨道分析及振动光谱分析。通过计算得知，靛蓝分子与靛玉红分子的所有原子均处于同一平面，两个分子都是由碳骨架及环上的氮原子参与的大的丌共轭体系构成，环上存在很强的离域。分子内存在较强的氢键，氢键与环上的碳碳键形成六元或七元环，使分子的各原子保持与吲哚环在同一平面并使分子的稳定性增加。     

卤键驱动的三元/四元大环自组装的研究

使用混合密度泛函PBE1PBE方法,在DGDZVP和DGDZVP-pp基组水平上研究了卤键驱动的(C_3H_2NI)_n,(C_5H_2NI)_n,(C_5H_4NI)_n,(C_7H_4NI)_n(n=3,4)进行自组装的结构与性质.结果表明:每个单体分子中静电势的极大值均位于碘原子处,静电势的极小值均位于氮原子处;增长碳链长度、增加自组装分子的个数可以使卤键的键长变短,键角更加趋近于180°,从而使卤键的强度增加,所形成的复合物更加稳定;溶剂的极性越大,复合物相对越不稳定;电子密度拓扑分析显示N…I之间所形成的卤键属于闭壳层的非共价相互作用.     

碳分子线（C2-C4）在单壁碳纳米管中结构的第一性原理研究

采用第一性原理的密度泛函理论,对碳分子线团簇（C2～C4）及其在单壁碳纳米管（SWCNT）（4,4）,（5,5）中的几何结构性质进行了计算模拟．发现碳分子线（C2-C4）在不同直径的单壁碳纳米管中的键长是不同的,结果将对碳纳米管内部的力学性质研究提供帮助．     

无机共轭分子的结构——Ⅲ.A_2B_4型分子

本文用LCAO MO法讨论了A_2B_4型无机分子的结构,具体地分析了包含34,36和38个价电子的A_2B_4型分手和离子的结构和性质。本文着重地研究了N_2O_4分子的键型,认为NN键具有σ性质和π性质,N_2O_4分子中存在Π_6~8键,NN距离比正常单键键长长0.27乃是由于O原子间凡德华斥力以及N原子间静电斥力所引起的。 N_2O_3分子在结构上与N_2O_3分子十分相似,本文也一并讨论。     

低维硼碳纳米材料第一原理研究

介绍了近年来关于低维硼碳纳米材料结构和电子性质的研究工作.通过第一原理计算,从理论上预言了稳定的低维硼纳米结构,并系统研究了以稳定硼平面为基础的硼纳米管和硼纳米带的电子性质.对于硼碳复合纳米材料,以BC3,BC5和BC7有序结构的平面为基础,发现对其剪裁、氢化修饰之后,硼碳纳米结构具有丰富的电磁学性质,可能在未来电子学器件中得到广泛的应用.     

水杨醛甘氨酸Schiff碱的从头算构象研究

运用从头算HF方法对水杨醛甘氨酸Schiff碱的构象进行了理论研究.结果表明,C=N键与苯环的共轭以及分子内弱相互作用是分子能量降低的2个重要结构因素.在各存在形态的所有最稳定构象中c=N键均与苯环共轭,均至少存在1条H14的弱氢键.酸式结构最稳定构象羧基上羟基氢H22背离大共轭平面;酸根形态的稳定构象羧基与苯环共面形成平面分子,且存在2条氢键;钾盐酚式最稳定构象羧基螯合成键,而醌式最稳定构象为平面分子,羧基单齿成键,且存在H14的2条弱氢键.由于具有很大的能量优势,水杨醛甘氨酸Schiff碱在水中的主要存在形态为酸式,该结论与其水溶液的实验研究结果一致.     

环丙烷与卤化氢相互作用本质的理论研究

在MP2/Sadlej pVTZ水平对环丙烷(C3H6)与卤化氢(HX,X=F,Cl,Br,I)分子的1∶1复合物进行几何结构优化,最稳定结构为HX分子几乎与环丙烷的碳环位于同一平面,且其氢原子指向环丙烷的一个碳碳弯键的中点.此外,渐近修正对称匹配微扰理论(DFT-SAPT)能量分解结果说明静电、诱导和色散力对描述此类弯键复合物都很重要,从HF到HI,静电能占总吸引作用能的百分比逐渐减少,色散能占总吸引作用能的百分比逐渐增加.     

单壁碳纳米管热稳定性的模拟研究

运用紧束缚近似分子动力学模型,模拟研究了各种单壁碳纳米管(SWCNTs)在300~4 000 K范围内的热稳定性.结果表明:手性碳管的热稳定性明显优于其它类型的碳管,半径相近的单臂管比锯齿管更稳定.在深入分析碳纳米管内碳键结构的基础上,进一步探讨了各种碳管的碳键从sp2向sp3转变的情况,利用键重构对碳管的热稳定性给出了理论解释;通过平均能量和温度的关系曲线分析,研究碳管热稳定性的变化.     

1,1,1-三甲胺基甲酰亚胺分子结构的量化计算

采用量子化学中的DFT/B3LYP和MP2方法研究了1,1,1-三甲胺基甲酰亚胺HC(＝O)N^-N⁺(CH₃)₃的分子结构,在计算得到的平衡几何构型基础上进行了分子轨道(MO)和自然键轨道(NBO)计算。通过几何构型全优化,发现该分子存在Z型(顺式)和E型(反式)2种异构体,2种异构体中都存在一个对称平面,胺基酰亚胺官能团C(＝O)N^-N⁺位于这个对称平面上。分子的几何结构参数及MO和NBO分析都表明在这2种异构体中,N^-的p轨道孤对电子都与羰基π键存在很强的共轭效应,Z型异构体中存在2个强度较弱的分子内氢键O…H—C。由分子总能量、离域π键的强度和H键可以表明Z型异构体比E型异构体更稳定。     

Infrared Spectroscopic and Theoretical Studieson Cobalt ( Ⅱ ) Complex of Maleinitriledithiolate and 4, 4f-Dimethyl-2, 2'-bipyridine

The complete experimental IR spectra and vibrational analysis of the title complex Co(mnt)(dmbpy) were reported in this paper. The results show that the complex molecule has a planar geometrybelonging to point group C2v and ground electronic state with spin quartet. A new method for analyzing vi-brational spectra of complicated molecule is established. The essential of this method is to point out mainfixed points and pivotal vibrational units in assignment for each fundamental band. Two new symbols q(heaving along the specified direction) and M (midpoint of a bond or unit) were defined for describing thevibrational modes accurately.     

新型超硬材料I-4碳的第一性原理研究

应用基于粒子群优化算法的卡里普索(CALYPSO)晶体结构预测方法 ,发现了一种新型的具有四方结构的C的同素异形体,空间群为I-4,将其命名为I-4碳.利用基于密度泛函理论的第一性原理计算方法对I-4碳的电子能带结构、电子态密度、声子谱、弹性常数以及体弹模量进行研究.计算结果发现:I-4碳动力学稳定,并且具有较大的体弹模量(432.12 GPa)和剪切模量(488.46 GPa);同时,从理论上算出其维氏硬度值可达到83.35 GPa.计算结果表明:I-4碳有望成为一种潜在的超硬材料.     

Infrared spectroscopic and theoretical studies on cobalt (II) complex of maleinitriledithiolate and 4, 4′-dimethyl-2, 2′-bipyridine

The complete experimental IR spectra and vibrational analysis of the title complex Co(mnt) (dmbpy) were reported in this paper. The results show that the complex molecule has a planar geometry belonging to point groupC _2v and ground electronic state with spin quartet. A new method for analyzing vibrational spectra of complicated molecule is established. The essential of this method is to point out main fixed points and pivotal vibrational units in assignment for each fundamental band. Two new symbols π (heaving along the specified direction) andM (midpoint of a bond or unit) were defined for describing the vibrational modes accurately. Foundation item: Supported by the National Natural Science Foundation of China (No. 29771025) Biography: Peng Zheng-he(1945-), male, Professor, research direction: functional materials & physical inorganic chemistry.     

La3和La4分子的结构与性质分析

在La原子的相对论有效原子实势下,用密度泛函B3LYP方法对La3分子和La4分子的各种可能的结构进行优化计算.结果表明,La3分子有3种稳定结构,其中D3h结构最稳定,为基态.La4分子存在10种稳定结构,其中平面C2V结构最稳定.详细讨论了Td构型和D4h构型的Jahn-Teller效应,结果表明,它们的各种畸变方式都符合群的分解原理.     

Production of Poly(3-Hydroxybutyrate-co-3-Hydroxyhexanoate) Using Aeromonas hydrophila 4AK4 Grown in Mixed Carbon Source

IntroductionPolyhydroxyalkanoates (PHAs) are intracellularenergy storage materials and/or reduction agentsthat are synthesized by many microorganisms[1 ] .Because these bacterial PHAs are trulybiodegradable thermoplastics or elastomers,theyhave attracted much attention in industry[2 ,3 ] .Poly(3 -hydroxybutyrate) (PHB) wasthefirst PHA to beproduced on a large scale and poly (3 -hydroxybutyrate-co-3 -hydroxyvalerate) (PHBV)was laterused in commercial applications.Recently,novel PHA copo…     

有机锡化合物{(PhCH2)2Sn[4-NC5H4CON2C(CH3)CO2](H2O)}2的合成及晶体结构

合成了有机锡化合物{(PhCH2)2Sn[4-NC5H4CON2C(CH3)CO2](H2O)}.用X-射线单晶衍射测定了该化合物的晶体结构,结果表明,在该配合物的晶体中,锡原子呈五配位畸变三角双锥构型.     

平面双核酞菁钴修饰电极的制备及催化性能研究

用电化学生长法将平面双核酞菁钴(bi-CoPc)修饰到玻碳电极(GC)的表面,制成化学修饰电极,用循环伏安法对该电极的电化学行为进行了研究.结果表明:化学修饰电极对溶液中的O2具有很好的电催化活性,当pH＜3时,可以经过两步四电子催化将O2还原成H2O;在碱性溶液中对巯基乙醇(2-ME)亦具有很好的电催化活性.     

Ge/Si nanowire heterostructures as high-performance field-effect transistors

Semiconducting carbon nanotubes and nanowires are potential alternatives to planar metal-oxide-semiconductor field-effect transistors (MOSFETs) owing, for example, to their unique electronic structure and reduced carrier scattering caused by one-dimensional quantum confinement effects. Studies have demonstrated long carrier mean free paths at room temperature in both carbon nanotubes and Ge/Si core/shell nanowires. In the case of carbon nanotube FETs, devices have been fabricated that work close to the ballistic limit. Applications of high-performance carbon nanotube FETs have been hindered, however, by difficulties in producing uniform semiconducting nanotubes, a factor not limiting nanowires, which have been prepared with reproducible electronic properties in high yield as required for large-scale integrated systems. Yet whether nanowire field-effect transistors (NWFETs) can indeed outperform their planar counterparts is still unclear. Here we report studies on Ge/Si core/shell nanowire heterostructures configured as FETs using high-kappa dielectrics in a top-gate geometry. The clean one-dimensional hole-gas in the Ge/Si nanowire heterostructures and enhanced gate coupling with high-kappa dielectrics give high-performance FETs values of the scaled transconductance (3.3 mS microm(-1)) and on-current (2.1 mA microm(-1)) that are three to four times greater than state-of-the-art MOSFETs and are the highest obtained on NWFETs. Furthermore, comparison of the intrinsic switching delay, tau = CV/I, which represents a key metric for device applications, shows that the performance of Ge/Si NWFETs is comparable to similar length carbon nanotube FETs and substantially exceeds the length-dependent scaling of planar silicon MOSFETs.     

Nanostructured LiMn2O4 and their composites as high-performance cathodes for lithium-ion batteries

Improvement of the energy density and power density of the lithium-ion batteries is urgently required with the rapid development of electric vehicles and portable electronic devices. The spinel LiMn2O4 is one of the most promising cathode materials due to its low cost, nontoxicity, and improved safety compared with commercial LiCoO2. Developing nanostructured electrode materials represents one of the most attractive strategies to dramatically enhance battery performance, such as capacity, rate capability and cycling life. Currently, extensive efforts have been devoted to developing nanostructured LiMn2O4 and LiMn2O4/carbon nanocomposites to further improve the rate capability of lithium-ion batteries for high-power applications. In this paper, recent progress in developing nanostructured LiMn2O4 and LiMn2O4/carbon nanocomposites is reviewed, and the benefits to the electrochemical performance of LiMn2O4-based cathodes by using these electrode materials are also discussed.     

4—N—甲基苯乙烯吡啶盐类的非线性光学效应的研究

利用剑桥晶体数据库（SCD）数据,用MOPAC半经验程序AMI方法计算了含非对称中心的4－N－甲基苯乙烯吡啶盐类晶体分子的二阶极化率,并用CSD提高的晶体结构数据计算了该类化合物阳离子的平面性,探讨了该类化合物取代基的性质和分子的平面性对分子二阶极化率的影响。