Structure formation of sulfonated polyphenylquinoxalines in solution and in the solid state

Sulfonated polyphenylquinoxalines with different content of sulfo groups have been synthesized by polymer analogous reactions under different conditions. The rheological properties of these polymers in Nmethylpyrrolidone have been studied. The mechanical properties of films based on sulfonated polyphenylquinoxalines under uniaxial tension have been measured. The structures of the polymers have been examined by AFM.     

On correct nonlocal generalized theories of elasticity

The paper discusses nonlocal elasticity theories among which are models of media with defect fields, gradient elasticity theories, and hybrid nonlocal elasticity theories. Gradient theories are analyzed, and their correctness properties are examined. Applied theories that satisfy the correctness conditions are developed, and known applied gradient theories are verified for the correctness properties. A new nonlocal generalized theory has been developed for which the operator of balance equations is represented as the product of the equilibrium operator of classical elasticity theory and the Helmholtz operator. It is shown that this theory is one-parameter and is the only representative of hybrid models constructed by a complete system of equations for forces and moments. Unlike classical elasticity that is free from scale parameters characterizing the internal material structure, nonlocal elasticity theories naturally incorporate these parameters. That is why they are suitable for the modeling of scale effects and find application in the solution of numerous applied problems for heterogeneous structures with developed phase interfaces where the degree of influence of scale effects depends on the density of phase boundaries. Nonlocal continuum models are especially attractive for modeling the properties of various micro/nanostructures, elastic properties of composites and structured materials with submicron- and nanosized internal structures in which effective properties are to a great extent defined by the scale effects (short-range interaction effects of cohesion and adhesion). Generalized elasticity theories even for isotropic materials contain many additional physical constants that are difficult or impossible to determine experimentally. Applied models with a small number of additional physical parameters are therefore of great interest. However, the reduction of nonlocal theories aimed at reducing the number of additional parameters is a nontrivial task and may lead to incorrect theories. The goal of this paper is to study the symmetry properties in gradient theories, to analyze the correctness of gradient theories, and to develop applied one-parameter elasticity theories.     

Colloidal aspects relating to direct incorporation of TiO2 nanoparticles into mesoporous spheres by an aerosol-assisted process

Titania nanoparticles have been incorporated into spherical mesoporous silica powders by an aerosol-assisted synthesis process from both aqueous and ethanol-based precursor dispersions. Transmission electron microscopy (TEM) showed that the titania nanoparticles exist as single particles or small aggregates within the mesoporous carrier particles and analysis of the nitrogen adsorption isotherms proved that the pore blocking of the particles is small. Particle size and zeta potential measurements showed that the addition of tetraethoxysiloxane (TEOS), and also hexadecyl trimethyl ammonium bromide (C16TAB) induced flocculation of the TiO2 nanoparticles. The higher yield and narrower size distribution of the composite powder produced from ethanol-based dispersions compared to the aqueous dispersions could be related to a smaller degree of aggregation, indicated by rheological measurements.     

一水甲酸锂晶体二阶非线性光学系数的理论计算

采用有限场方法和含时耦合微扰方法,在6-31+G*基组水平上并考虑了电子相关效应和色散效应的影响,计算了一水甲酸锂晶体的宏观二阶非线性光学极化率和二阶非线性光学系数。其中非线性光学系数d31和d32与Roberts报道的相符,而另一个系数d33则比文献值大。计算结果还表明,在非共振情况下,电子相关效应对非线性光学极化率的影响远远超过了色散效应,同时表明Roberts报道的非线性光学系数比Singh等人报道的更为合理。     

Spectroscopic calculations of CH bond dissociation energies for ethene, propene, and benzene chlorine derivatives

CH bond dissociation energies have been determined by spectroscopic and quantum-chemical calculations for ethane, propene, and benzene chlorine derivatives. The spectroscopic values of CH bond dissociation energies were obtained from the fundamental absorption bands in an anharmonic approximation using the variation method and the Morse harmonic basis. Quantum-chemical calculations were carried out using the 6-311G(3df,3pd)/B3LYP basis. The resulting tendencies of variation of bond dissociation energies are discussed in relation to changes in the structure of the molecule.     

Tin Domain Growth on Quasi-Two-Dimensional CdTe and CdSe Nanoparticles

Tin domain growth on quasi-two-dimensional colloidal CdSe and CdTe nanoparticles having the zinc blende structure has been studied. The initial quasi-two-dimensional CdSe and CdTe nanoparticles having lateral sizes of 100–200 nm were prepared by a colloidal method. Tin domain growth was accomplished in tetrahydrofuran via the reduction of a tin(II) salt by tetrabutylammonium borohydride. The tin domains had sizes of 10–20 nm as probed by TEM. In case of CdSe nanoparticles, tin domains were grown inside the inner cavities of initially rolled nanoparticles. A β-tin phase was identified by X-ray diffraction. The absorption spectra featured the broadening of exciton bands corresponding to quasi-two-dimensional nanoparticles, the spectral positions of absorption peaks remaining almost unchanged.     

Theoretical Studies on the Binding of Cd~（2＋） to Uracil and Its Thio-derivatives

The interaction of Cd2+ with uracil,2-thiouracil,4-thiouracil and 2,4-dithiouracil have been investigated by the density functional theory(DFT) calculations.For uracil and 2,4-dithiouracil,where the two basic sites are the same,Cd2+ attachment to the heteroatom at position 4 is preferred.However,for the systems where both types of basic centers,a carbonyl and a thiocarbonyl groups,are present,Cd2+ association with sulfur is favorable.The enhanced stability of these enolic and thiol forms comes from Cd2+ interaction with two basic sites simultaneously,which thereby triggers a significant aromatization of the ring.More significantly,the Cd2+ binding energy with uracil and its thio-derivatives is larger than the tautomerization barriers connecting the diketo-like forms with the corresponding enolic-like tautomers.Consequently,when associated with Cd2+,all tautomers are energetically accessible and should be observed in the gas phase.     

过渡金属类立方烷原子簇化合物电子结构和二阶非线性光学性质的密度泛函理论研究

采用基于第一原理的含时密度泛函理论(TDDFT)对一系列具有类立方烷簇芯结构的过渡金属簇合物二阶非线性光学性质进行了研究。结果证明, 由于簇芯结构的对称性的影响, 这一类簇分子的二阶非线性光学系数的数值要小于三核欠完整类立方烷体系。通过对电子结构的分析, 发现二阶非线性光学性质主要是由簇芯内电荷的迁移造成的。轨道分析显示, -S原子对于电荷的迁移起主要的传递作用。定域化轨道分析证明簇分子中存在的多中心键有利于簇芯内电荷的迁移。分子模拟的研究表明:虽然类立方烷结构簇分子的值比较小, 但是通过合理的配体设计, 获得具有较大值非线性光学晶体是可能的。     

LAP晶体二阶NLO响应电子起源理论研究

L-精氨酸磷酸盐(L-Arginine Phosphate Monohydrate, LAP)晶体，是一种有应用潜力的无机－有机杂化NLO晶体材料[1, 2]。Eimerl等人认为LAP晶体二阶NLO响应主要源于L-精氨酸分子(Arg )，磷酸根(H2PO4－)对LAP晶体宏观NLO响应没有重要贡献[2]；而许东等人认为，LAP晶体的NLO响应是由L-精氨酸分子和磷酸根共同贡献的结果[1]。本通讯通过第一原理从头算计算，揭示了LAP晶体二阶NLO响应的电子起源。 表1. 激发态性质 Table 1. The Excited States at CIS/STO-3G Level (Dmge in Debyes; l in nm; (rx)ge in au) States…     

Crystal and Molecular Structure of Monoammonium Salt of 5‐nitroaminotetrazole

Xray structural investigation of the monoammonium salt of 5nitroaminotetrazole was performed. The crystals are orthorhombic: a = 10.077(1), b = 17.009(1), c = 6.6472(6), V = 1139.33(17)³, space group Pbca, Z =8, _calc = 1.715 g/cm³. Monodeprotonation of 5nitroaminotetrazole during formation of the salt occurs at the N(4) nitrogen atom of the heterocycle. The anion has an almost flat structure; the bond lengths suggest delocalization of electron density in the molecule. The negative charge is distributed among three nitrogen atoms and two oxygen atoms of the anion. Changes in the geometrical parameters of 5nitroaminotetrazole on monodeprotonation are considered.