直链共轭高分子的分子轨道理论——Ⅳ.一维重复单胞体系本征方程的单频约化条件

本文给出了直链共轭高分子体系中,底向量D(λ)的相角与高分子局部对称性之间的关系。并在此基础上,找到了共轭高分子体系本征方程的单频约化条件。     

直链共轭高分子的分子轨道理论(Ⅳ)——一维重复单元体系本征方程的单频约化条件及体系的边界态

对于由重复单元构成的体系,如何利用其准周期性及局部对称性约化本征方程一直是一个人们感兴趣的课题。本文作者已发表3篇文章讨论有关的问题。其中,利用差分方程方法处理直链共轭高分子体系时,涉及如下方程:     

共轭高分子体系的分子轨道理伦V:二维重复单胞体系本征方程的因子分解方法

本文将一维重复单胞体系本征方程的因子分解方法向二维体系作了一般的推广,从而解决了一些重复单胞构成的二维大分子体系的能谱问题 , 利用因子分解法,本文研究了石墨二维平面分子边缘的化学反应活性以及体系的电子结构, 导电性与分子尺度的关系, 结果表明, 对于石墨类分子, 边界效应是非常显著的, 且体系的反应活性, 导电机制与边界的结构紧密相关。     

具有重复单元的共轭分子的量子化学计算及其应用(下)

三、同系线性规律关于同系线性规律国内许多科学工作者都做过工作,首先从实验中总结了一些规律,也有从量子化学上加以理论推导。所谓同系分子就是指同一类分子只是重复单元数不同,例如多烯烃,两个碳是乙烯,四个碳是丁二烯,六个碳是已三烯等等,就属于同系列的。具体还可分偶多烯烃和奇多烯烃,这里讨论的奇多烯烃实际是自由基,因此偶的为一类,奇的为一类。对多炔烃也是一样有奇偶之分。对同系物还可以有不同的端基,如—CHO;—COOH等。对同系物分子而言,它的某些物理性质同n的一个函数F(n)有关(n代表重复单元数目),其中有些性质和这个函数成直线关系,称为同系线性规律。但不是所有物理性质都有同系线性规律,     

共轭高分子体系的分子轨道理伦V:二维重复单胞体系本征方程的因子分解方法

本文将一维重复单胞体系本征方程的因子分解方法向二维体系作了一般的推广,从而解决了一些重复单胞构成的二维大分子体系的能谱问题 , 利用因子分解法,本文研究了石墨二维平面分子边缘的化学反应活性以及体系的电子结构, 导电性与分子尺度的关系, 结果表明, 对于石墨类分子, 边界效应是非常显著的, 且体系的反应活性, 导电机制与边界的结构紧密相关。     

分子轨道图形理论中对称轴定理

本文试图以浅显明确的形式描述对称轴定理，使之能与对称面定理相媲美，并对对称轴定理作一定的扩展，给出分子轨道构造定理。     

Wick定理及约化密度矩阵的重构方案

利用外积获得了Wick定理的封闭表达式, 并给予了严格的证明. 新的表示式类似于二项式展开. 利用这一新形式, 推导出了约化密度矩阵的重构方程. 高级约化密度矩阵系统地分解为低级约化密度矩阵的和. 有了这些重构方程便可以求解简宿Schrödinger方程(contracted Schrödinger equation).     

价电子对互斥理论与电价理论相结合判定分子的共轭类型

以价电子互斥理论与杂化轨道理论为基础,首先确定中心原子或离子的杂化类型以及总电子对的结构,并确定处于同一平面的原子;然后摒除σ键,仅分析π键,并根据价键理论,确定参加共轭的原子对共轭π键所贡献的电子数,最终达到对分子共轭类型的判别。     

Atop-the-barrier localization in periodically driven double wells: A minimization of information entropic sums in conjugate spaces

The spatio-temporal localization of a system in the presence of an oscillating electric field for a symmetric double-well potential is examined via numerical simulations of the time-dependent Schrödinger equation. For an initial state with equal probability densities in both the wells, stabilized localization atop the barrier can be achieved on a periodic high-frequency driving. The barrier localization is characterized using Shannon information entropies in position and momentum spaces, defined as S_ρ = − ∫ |ψ|² ln |ψ|² dx and S_γ = − ∫ |ϕ|² ln |ϕ|² dp , where ψ and ϕ refer to position and momentum space wave functions, respectively. The information entropy sum, S_ρ + S_γ, goes through a minimum indicating the formation of the barrier-localized state, when the peak intensity of the oscillating field is reached. The generalized uncertainty via the Białynicki-Birula-Mycielski inequality ( S_ρ + S_γ ≥ 1 + lnπ ) is saturated upon this minimization. This serves as a signature of the formation of the barrier-atop localized state, in terms of Shannon entropies of measurable densities.     

The calculation of vibrational energy levels of polyatomic molecules including anharmonic effect using contact transformation perturbation method

Using contact transformation perturbation method based on the Taylor expansion of the potential energy function in terms of dimensionless normal coordinates up to sixth‐order, the vibrational energy levels in terms of force constants are derived. The contact transformation theory has been applied to simplify the calculation of perturbation effects. To calculate the second‐order vibrational energy correction, the third and fourth‐order terms of potential function have been placed in the first‐order perturbation Hamiltonian and the second‐order Hamiltonian contains hexatic ones. We present expressions which give relations between the fourth‐ and sixth‐order terms in dimensionless normal coordinates of the potential and the anharmonicity coefficients. For illustration, a set of vibrational energies levels of SO₂, and H₂O molecules including anharmonic effects has been calculated. © 2013 Wiley Periodicals, Inc.     

The delocalisation energy of benzene and the non-empirical MO theory

Algebraic expressions for the vertical Delocalisation Energy (DE) of benzene are derived from non-empirical MO theory. For comparison with early work in the π-electron approximation, and ultimately with Hückel theory, the results are formulated in terms of a core resonance integral,β, and π-electronic repulsion integrals. All integral values are inferred from the results ofab initio SCF calculations. Two expressions are derived, which refer to two ways of forming the localised π MOs: one where three pairs of adjacent atomic orbitals are selected from a set of six orthogonalised orbitals; and another where a non-orthogonal set of atomic orbitals is used. The first expression is formally similar to an expression originally derived by Pople from a different point of view and with many approximations. This expression gives too large a magnitude for DE when used with anab initio value ofβ. The second expression gives a result much closer to an empirical value of DE and shows that the main reason for DE being about 50% of 2β rather than 2β is the stabilising effect of overlap in the localised structure, and that the less important factor is the inclusion of electronic repulsion.     

Synthesis and biodistribution of bowman-birk soybean protease inhibitor conjugate with amphiphilic polyester

The modification of Bowman-Birk soybean protease inhibitor (BBI) with the monoaldehyde derivative of block copolymer of ethylene oxide and propylene oxide (PE),M _r 2000 is described. The conjugate contains five covalently bound polymer chains per protein molecule, and retains the ability to inhibit trypsin and chymotrypsinlike proteinases. The distribution of native BBI and the BBI-PE conjugate was examined in mice. After iv injection of [¹²⁵I]BBI and [¹²⁵I]BBIPE, both inhibitors distributed very rapidly to the liver, kidney, and lungs, and more slowly to the brain. At the same time-points (up to 24 h), radioactivity in the blood and organs of mice injected with modified inhibitor was higher than that of the native inhibitor. The blood concentration time profile following iv administration of two BBI preparations at a dose 3 mg/kg was reasonable well described by a two-compartment open model with first-order elimination kinetics. The total clearance of BBI-PE decreased by a factor of 8, body mean residence time increased by a factor of 5 in comparison with BBI. A physiological pharmacokinetic model was developed to describe the tissue-to-blood distribution of two inhibitors. One-compartment physiological organ model (flow limited) was used to describe of timecourse profiles of BBI concentration in organs. A two-compartment physiological organ model (membrane limited) was used to predict tissue-to-blood distribution of conjugated BBI in some organs of mice (liver, lungs). The predicted concentration curves of BBI and BBI-PE in blood and organs in mice (with the exception of kidney) showed good agreement with the observed values.     

Quantum manifestations of classical trajectories in molecular systems

Quantum chaos, understood as the effect of the underlying classical dynamics on the stationary quantum properties in classically chaotic systems, is examined in two molecular floppy systems. Realistic models of two degrees of freedom for HO₂ and HCN/HNC are considered. The structure of the classical phase space is studied using Poincaré surfaces of section and the dynamical characteristics of the corresponding wave functions analyzed also in phase space with the aid of Husimi functions. Some wave functions show strong localization along periodic orbits. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem, 2001     

Simulation of the bioadhesive gelatin‐alginate conjugate loaded with antibiotic drugs

In the present research, molecular modeling methods were used to study a novel bioadhesive composed of gelatin (protein) and alginate (polysaccharides), crosslinked with N‐(3‐dimethylaminopropyl)‐N′‐ethylcarbodiimide hydrochloride (EDC) and N‐hydroxysuccinimide (NHS). Three antibiotic drugs were added to the bioadhesive: Vancomycin, Ofloxacin, and Clindamycin. Computational tools were applied to estimate the crosslinking degree and compare the effect of the antibiotics on the physical properties of the gelatin‐alginate conjugate. The crosslinking degree was estimated by calculating the enthalpy of mixing of gelatin with alginate and their interaction with the crosslinking agents. The calculations revealed that gelatin mixes well with alginate, which enables their crosslinking. Various ratios between EDC and NHS were examined, and an optimal ratio was found. The interaction of alginate‐gelatin conjugate with the antibiotics was correlated to the experimental results of bonding strength. The most significant interaction of the conjugate is with clindamycin. The gelatin part is responsible for the strong interaction with clindamycin, and alginate forms strong interaction with ofloxacin. Thus, the interaction of alginate‐gelatin conjugate with the antibiotics is governed by the proportion between gelatin and alginate in the conjugate. The degradation rate of gelatin‐alginate was related to its interaction with water. It was found that the conjugate is highly hydrophilic. Gelatin is more soluble in water than both alginate and alginate‐gelatin and is probably the part in the conjugate that governs the solubility and degradation rate. Therefore, the degradation rate of the conjugate can be controlled by changing the proportion between gelatin and alginate.