C12簇及其碳管烷C12H12的理论研究

C60和C70等碳笼烯的发现及其在新物质、新材料等研究领域中的重要性，激励人们去探索合成更多新型多面体碳簇化合物与碳元素类似物[1，2]．最近，两类新型多面体碳管笼烯的设想提出来了[3，4]应用HMO和MNDO方法对其稳定性变化规律、结构和成键特征进行了讨论.关于多苯的vanderWaals簇实验上已有广泛的调查[5，6]，理论上对其二聚物（C6H6）。的不同几何构型与稳定性进行了深入的研究[7]．本文采用abinitio计算有效势（effectivecorePotential）方法，对C12碳管元素簇和C12H12，碳管烷的平衡结构、稳定性和价键特征进行了理论预测．1…     

Effect of substituents (NH_2,OH,F) on structures and stability of lithofluorosilylenoids

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Structure and stability of thiourea with water, DFT and MP2 calculations

The relative stabilities of thiourea in water are investigated computationally by considering thiourea–water complexes containing up to 1–6 water molecules (CS(NH₂)₂(H₂O)_n=1–6) using density functional theory and MP2 ab initio molecular orbital theory. The results show that the thiourea complex is stable and has an unusually high affinity for incoming water molecules. The clusters are progressively stabilized by the addition of water molecules, as indicated by the increasing of the binding energy. The binding energy of the cluster to each H₂O molecule is about 33 kJ mol⁻¹ for n=1–5.The C–S bond, N–C bond distance, Mulliken populations and binding energy keep approximately constant as the clusters increase in size with an increasing number of H₂O molecules. As the solvation progresses, the C–S distance increases monotonically while the Mulliken populations on the C–S bond reduces monotonically with the addition of each H₂O molecule, indicating that the C–S bond of the thiourea unit in the clusters is de-stabilized with an increasing number of H₂O molecules. Charge transfers for the clusters are mainly found at N, S atoms of the thiourea.     

Significance of Non-isothermal Kinetic Data. A statistical study

Arrhenius parameters values, in non-isothermal kinetic vaporisation processes for a series of compounds with related structures, have been calculated. This was made using a method of calculation that allows to find the most probable vaporisation mechanisms. According to this method DTG curves were compared with some theoretical ones reported in literature, whose shape results to be only a function of the mechanisms. In this way the choice of the mathematical functions which can be inserted in the kinetic equations, was influenced by the shape of the DTG plots and other thermal analysis signals thus allowing to choose the most probable mechanisms. The kinetic parameters derived from these mechanisms were compared, using statistical analysis, with those obtained from another method of calculation based on ‘a priori’ vaporisation mechanism chosen for the investigated liquid–gas transition. The standard deviations of the slope and of the intercept, together with the standard deviation and the square correlation coefficient (r ²) of the linear regression equations related to the mechanisms of the two methods were calculated. Student t-test, Fisher F-test, confidence intervals (c.i.) and residuals valueswere also given. Statistical analysis shows that the mechanisms obtained with the former method (diffusive and geometrical models) and the related Arrhenius parameters result to be more significant (in terms of probability) than the corresponding quantities of the latter for which a first-order model was chosen. This revised version was published online in August 2006 with corrections to the Cover Date.     

Spectroscopy, NMR and DFT studies on molecular recognition of crown ether bridged chiral heterotrinuclear salen Zn(II) complex

A barium-containing crown ether bridged chiral heterotrinuclear salen Zn(II) complex BaZn2L(ClO4)2, where L is a folded dinuclear chiral (R,R)-salen ligand, has been synthesized and characterized by elemental analysis, 1H NMR, UV-vis, IR, circular dichroism (CD) spectra, and mass spectra. As a folded dinuclear chiral host, its recognition with achiral guests (imidazole derivatives), rigid bidentate guest (1,4-diazobicyclo[2,2,2]octane, DABCO) and chiral guests (amino acid methyl esters) was investigated by means of UV-vis spectrophotometric titration, CD spectra. The association constants of D-amino acid methyl esters are found to be higher than those of their L-enantiomer. The sandwich-type binding of BaZn2L(ClO4)2-DABCO supramolecular assembly was specially studied via 1H NMR titration and 1H ROESY. To understand the recognition on molecular level, density functional theory (DFT) calculations on B3LYP/LanL2DZ were performed on the minimal energy conformations of host, guests, and host-guest complexes. The minimal energy conformations were obtained by molecular mechanics (MM) optimization and molecular dynamics (MD) simulation. The results of single point energy, HOMO energy, and charges transfer were analyzed. The results of theoretical calculations are in good agreement with the experimental data.     

Insight into the cation–anion interaction in 1,1,3,3-tetramethylguanidinium lactate ionic liquid

In order to deepen the understanding of cation–anion interaction in ionic liquids (ILs), the structure and interionic interaction of 1,1,3,3-tetramethylguanidinium lactate ([tmg][L]) ion pair, including stable configuration, hydrogen bond, frontier molecular orbital, electron density, ion interaction energy and charge transfer, are studied by using ab initio calculations. It is found that more charge-localized character of [tmg][L], especially the C1 carbocation on [tmg]⁺, and the intermolecular –NH₂-associated hydrogen bonds can substantially increase the cation–anion interaction, the interaction energy is 65.3–109.3 kJ/mol higher than that of 1-n-butyl-3-methylimidazolium-based ILs. It is also found that the frontier molecular orbitals, i.e., the HOMO, HOMO + 1 of [L]⁻ and the LUMO, LUMO + 1 of [tmg]⁺, can effectively interact and more charges are transferred between cation and anion. Based on the above results, the physical property of ILs is discussed.     

Experimental and density functional studies on two structurally similar antipyrine derivatives: 4-(2-hydroxy-5-nitrobenzylidene-amino)-1,2-dihydro-1,5-dimethyl-2-phenylpyrazol-3-one and 4-(3-bromo-5-chloro-2-hydroxybenzylideneamino)-1,2-dihydro-1,5-dimethyl-2-phenylpyrazol-3-one

The Schiff base compounds, 4-(2-hydroxy-5-nitr- obenzylideneamino)-1,2-dihydro-1,5-dimethyl-2-phenylpy- razol-3-one and 4-(3-bromo-5-chloro-2-hydroxybenz- ylideneamino)-1,2-dihydro-1,5-dimethyl-2-phenylpyrazol-3-one, have been synthesized and characterized by elemental analysis, IR, and X-ray single crystal determination. Density functional calculations of the structures, natural bond orbitals, and frontier molecular orbitals and Mülliken charge analysis on the compounds were performed at B3LYP/6-31+G(d) level of theory. Vibrational frequencies were also predicted, assigned, and compared with the experimental values, which supported each other.     

锌族和钛族卤化物振动光谱的理论计算

采用ab initio RHF,MP2和B3LYP方法以及LanL2DZ和SDD基组计算了四面体锌族卤素阴离子化合物(MX₄^2-,M=Zn(Ⅱ),Cd(Ⅱ),Hg(Ⅱ);X=F^-,Cl^-,Br^-,I^-)和钛族卤化物(MX₄,M=Ti(Ⅳ),Zr(Ⅳ),Hf(Ⅳ);X=F^-,Cl^-,Br^-,I^-)的几何构型和振动频率。计算结果表明,LanL2DZ基组是合适的基组,能得到合理的电荷分布,几何参数以及振动频率。在锌族卤化物的计算中发现,角弯曲振动频率与实测值相当一致,键伸缩振动频率略为偏低,这主要是由于计算的键长略为偏长所致。MP2方法计算的振动频率更接近于实测值。在钛族卤化物的计算中,三种计算方法都相当地再现了实测值,而以B3LYP方法更为满意。     

粉末高温合金平衡相析出行为的热力学对比

利用热力学平衡相计算方法及相应的高温合金数据库对René95,Rene88DT和эп741нп三种合金在平衡相析出温度范围和析出量以及之间的关联性进行了系统的热力学计算对比分析.结果表明:三种粉末高温合金的平衡相种类基本相同,主要平衡相为γ,γ'和碳化物M23C6,MC,M6C.René95合金中的碳化物含量要高于其他两种合金.3п741нп有着较高的γ'相析出温度和较大的析出量.随温度降低,Co和Nb从γ'相中析出,在其周围富集,其中3п741нп合金中尤为明显.合金元素的偏聚度也和合金的初熔点与终熔点之差的大小有关,其熔解区间越大即初熔点和终熔点之差越大,合金元素的偏聚度越大.     

外微分在场论中的应用

建立了外微分理论与场论之间的一些对应法则，指出外微分形式是场论中众多命题的数学模型，得到用外微分运算解决场论中梯度、旋度、散度以及环量与通量的计算和几种重要的矢量场：梯度场、旋度场、调和场证明的新方法。为利用计算机处理这类问题提供了一种简单模式，从而实现求解问题的机械化算法。