The simplest model of adsorption of molecules with different orientations in adlayer on the stepped surface

In this article we have constructed and studied using the Monte Carlo and transfer-matrix techniques the simple lattice gas models of self-assembled monolayer, which consists of molecules with different orientations in the adlayer on the stepped surfaces. It was shown that in the case of adsorption of complex molecules the surface heterogeneity of stepped type leads to a great variety of ordered structures comparatively with homogeneous one. The constructed models fairly well reproduce the main features of real SAMs consisting of molecules with different orientations with respect to interface and the model ordered phases are also analogues to the structures of real SAMs.     

Effect of electroelastic anisotropy of DNA-like molecules on their tertiary structure

Under certain conditions, mechanical forces can cause an anisotropic molecule like DNA to assume a toroidal spatial structure. A simple model describing such a behavior is suggested. The model incorporates anisotropic elastic energy and external electrical forces. The steady-state structures formed by a macromolecule have been studied numerically using this model. There exist ranges of model parameters, namely, the anisotropy of the elastic tensor, magnitude and orientation of forces, and modulation periods, where molecules have toroidal, spherical, or extended structures. Estimates of parameters characteristic of these structures are consistent with experimental data. In particular, the toroidal structure dimension corresponds to experimental dimensions of toroidal globules produced as a result of so-called PSI condensation of DNA molecules. Zh. éksp. Teor. Fiz. 112, 2156–2168 (December 1997)     

带电荷C60分子的电子结构及其非线性光学性质

应用Su-Schrieffer-Heeget(SSH)模型研究带电荷C₆₀分子的结构和电子结构.分析所带电荷量对结构的影响,计算带不同电荷数时C₆₀分子的电子结构,进一步对三阶非线性光学极化率进行了研究.     

氢键对2-(N-甲基)氨基-5-硝基吡啶分子非线性光学性质的影响

本文在杂化密度泛函理论水平上研究了溶剂对2-(N-甲基)氨基-5-硝基吡啶分子非线性光学性质的影响.在溶剂中,构造了包括氢键作用的超分子体系,在优化结构的基础上分别研究了由极化连续模型模拟的溶剂与该分子的长程相互作用、溶剂与该分子的氢键相互作用以及溶剂与包括氢键作用的超分子体系整体的相互作用对分子的几何结构、非线性光学性质、紫外吸收光谱和电荷分布等特性的影响.结果表明,溶剂中分子电偶极矩、线性极化率和第一超极化率都增大,而溶剂与溶质分子通过氢键形成的超分子结构与单体有着明显区别.因此,氢键对分子结构和性质的影响较大,从而将明显的影响该类分子的非线性光学性质.     

The octet rule in chemical space: generating virtual molecules

We present a generator of virtual molecules that selects valid chemistry on the basis of the octet rule. Also, we introduce a mesomer group key that allows a fast detection of duplicates in the generated structures. Compared to existing approaches, our model is simpler and faster, generates new chemistry and avoids invalid chemistry. Its versatility is illustrated by the correct generation of molecules containing third-row elements and a surprisingly adept handling of complex boron chemistry. Without any empirical parameters, our model is designed to be valid also in unexplored regions of chemical space. One first unexpected finding is the high prevalence of dipolar structures among generated molecules.     

Pattern formation and localized structures in reaction-diffusion systems with non-Fickian transport

We study the robust dynamical behaviors of reaction-diffusion systems where the transport gives rise to non-Fickian diffusion. A prototype model describing the deposition of molecules in a surface is used to show the generic appearance of Turing structures which can coexist with homogeneous states giving rise to localized structures through the pinning mechanism. The characteristic lengths of these structures are in the nanometer region in agreement with recent experimental observations.     

Application of the intersecting spheres model to periodic structures: Computation of the energy bands of diamond

The intersecting spheres model is an asymptotically exact method for the solution of the X_α equations which has already been applied to molecules with satisfactory results. This success led us to extend the model to the case of periodic structures. The results of a calculation of the self-consistent energy bands of diamond are reported here in order to show the capability of the model to deal with crystalline structures.     

Lie Symmetries and Conserved Quantities for Super-Long Elastic Slender Rod

DNA is a nucleic acid molecule with double-helical structures that are special symmetrical structures attracting great attention of numerous researchers. The super-long elastic slender rod, an important structural model of DNA and other long-train molecules, is a useful tool in analysing the symmetrical properties and the stabilities of DNA. We study the Lie symmetries of a super-long elastic slender rod by using the methods of infinitesimal transformation. Based on Kirchhoff＇s analogue, generalized Hamilton canonical equations are analysed. The infinitesimal transformations with respect to the radian coordinate, the generalized coordinate, and the quasimomentum of the model are introduced. The Lie symmetries and conserved quantities of the model are presented.     

Structure properties and Noether symmetries for super-long elastic slender rod

DNA is a nucleic acid molecule with double-helical structures that are special symmetrical structures attracting great attention of numerous researchers. The super-long elastic slender rod, an important structural model of DNA and other long-train molecules, is a useful tool in analysing the symmetrical properties and the stabilities of DNA. This paper studies the structural properties of a super-long elastic slender rod as a structural model of DNA by using Kirchhoff＇s analogue technique and presents the Noether symmetries of the model by using the method of infinitesimal transformation. Baaed on Kirchhoff＇s analogue it analyses the generalized Hamilton canonical equations. The infinitesimal transfornaationa with rcspect to the radial coordinnte, the gonarnlizod coordinates, and the Cluasi-momenta of 5he model are introduced. The Noether gymmetries and conserved qugntities of the model are obtained.     

Chemical shifts in photoelectron spectroscopy: indirect evaluation of the coulombic contribution to ionization potentials for non-bonding electrons

The ionization potentials assigned to non-bonding electrons of chlorine, bromine and oxygen in 96 molecules and 108 different structures are discussed. The Silberstein-Siegbahn model used with Smith—Ree—Magee-Eyring net charges appears to be a good approach for the calculation of the chemical shifts on complicated molecules. The easily computable Coulombic contribution to the ionization potential IP, seems to be the main one to account for the observed chemical shifts.     

Stabilization variation of organic conductor surfaces induced by π-π stacking interactions

The structures and stabilization of three crystal surfaces of TCNQ-based charge transfer complexes(CTCs) including PrQ(TCNQ) 2,MPM(TCNQ) 2,and MEM(TCNQ) 2,have been investigated by scanning tunneling microscopy(STM).The three bulk-truncated surfaces are all ac-surface,which are terminated with TCNQ molecular arrays.On the ac-surface of PrQ(TCNQ) 2,the TCNQ molecules form a tetramer structure with a wavelike row behavior and a γ angle of about 18° between adjacent molecules.Moreover,the dimer structures are resolved on both ac-surfaces of MPM(TCNQ) 2 and MEM(TCNQ) 2.In addition,the tetramer structure is the most stable structure,while the dimer structures are unstable and easily subject to the STM tip disturbance,which results in changeable unit cells.The main reasons for the surface stabilization variation among the three ac-surfaces are provided by using the ’π-atom model’.     

氮分子固体中配位环境对其分子振动的影响

研究了孤立氮分子与处于氮分子固体中氮分子之间的振动频率差异.基于α-N_2晶体结构建立了5种不同氮分子数的氮分子固体团簇模型,采用密度泛函理论计算了孤立自由氮分子及各固体模型中氮分子的振动频率,并对它们的频率进行了比较和讨论.比较发现:受集体效应的影响,处于分子固体模型中的所有氮分子的键长较孤立自由氮分子的键长更短,振动频率更高;就固体模型本身而言,分子数越多,平均振动频率越大,而且,内部氮分子的振动频率总是大于表面氮分子的振动频率,整体来说,频率大小关系为v_(内部)v_(表面)v_(孤立).讨论分析认为这种频率差异主要是由于孤立自由氮分子、固体表面和内部分子的配位关系不同引起的;表面分子存在大量配位缺陷,与其相互作用的分子相对较少,氮分子键力较弱,从而频率更低.     

Analytical model of light beam diffraction by one-dimensional electrically controlled non-uniform transmission photon PDLC structures

A mathematical model describing two-dimensional diffraction of quasi-monochromatic light beams by onedimensional electrically controlled non-uniform holographic photon structures in photopolymer dispersed liquid crystal (PDLC) materials is presented. The model describes light field distributions in the near and far field zones with allowance for the refractive index profile in the structure, light beam divergence, and encapsulation of liquid crystal molecules.     

Frustrated smectics: Theoretical phase diagrams in mean field

The model of J. Prost of frustrated smectic is presented and a review of the various phase diagrams calculated in the mean field approximation is given. Seven of the experimentally known structures are successfully interpreted and comparison with experiments shows that the topologies of the observed phase diagrams are remarkably well reproduced. This review suggests that this simple model of frustration with two coupled smectic order parameters describes correctly and completely the physics of strongly polar smectogenic molecules.     

Formation of Zero Density Regions During the Dissolving of C60 and C70

Based on a comprehensive review of the calculated and experimental data obtained in this and previous articles by the authors, a phenomenological model of the supramolecular structure of fullerene solutions is proposed. The model suggests the development in the fullerene solutions of some zero density regions due to poor packing of spheroidal fullerene molecules C₆₀ and C₇₀, on the one hand, and columnar or ribbon supramolecular structures formed by solvent molecules, on the other. It is assumed that the source of the long-range energy of fullerenes is a physical vacuum, concentrated not only in the cavities of the fullerene molecules but also in new regions forming outside the fullerenes during their dissolving in single-ring aromatic solvents.     

范德华作用和静电作用下的二元粒子自组装

采用简单粗粒化粒子模型,通过郎之万动力学模拟研究了具有范德华作用和静电作用的二元粒子自组装．研究发现,通过改变粒子尺寸和粒子间作用强度,二元粒子能够自发形成各种聚集结构,如球 形、堆叠层状与管状结构．利用两亲性分子或两嵌段聚合物自组装理论,解释了二元粒子聚集结构的形成规律．当向溶液中加入反电荷离子时,模拟表明粒子聚集结构在相图中的分布出现了明显偏移．     

Calculation and interpretation of the vibronic spectra of pyridine and <Emphasis Type="Italic">trans</Emphasis>-1,2-di(2′-pyridyl)ethylene in the second approximation of the parametric method

The structures of pyridine and dipyridylethylene molecules in an excited state and their vibronic spectra are calculated within the second approximation of the parametric method. The system of parameters obtained, including parameters of the σ and π types, ensures a quantitative agreement between the theoretical and experimental spectra of the pyridine and dipyridylethylene molecules. This agreement indicates that the proposed model is adequate to the real structure of the molecules. The parameterization is sufficiently complete and provides a means for quantitatively modeling the vibrational structure of the spectra of complex molecules containing fragments similar to those characterized by the σπ* and ππ* transitions. It is demonstrated that, after such essential substitutions of atoms in the molecules, the system of parameters of the acene and polyene fragments retains the high stability. The vibrational structure of the electronic spectra of the pyridine and dipyridylethylene molecules is interpreted, and the changes observed in the geometry of these molecules under electronic excitation are analyzed.     

染料LB膜吸收光谱和光学存储效应的研究

通过对新型的染料LB膜(花氰-花生酸复合LB膜)的吸收光谱的测试,说明了LB膜中染料分子H-聚体结构的存在,而在立体简并四波混频实验中观察到这种LB膜具有可逆的光学记录与擦除效应,实验表明,在其中建立一个稳定的光栅,所用的记录光脉冲强度为30MW/cm~2,需要的累积记录时间为80ns(10个脉冲).最后在简化的三能级系统中,以分子处于各态的布居光栅模型说明了光致H-聚体,单体之间的转化是这种光学记录效应的主要原因.     

Quantum Groups and Spectra of Diatomic Molecules

We briefly review and further investigate the quantum group theoretic approach to the spectra of the diatomic molecules presented by the authors recently. The vibration-rotational structures as well as the interactions of vibrations and rotations are described in the quantum group theoretic approach satisfactorily. When nylor expanded, the analytic formulae of the new approach reproduce the results of nonlinear vibratingrotator model. For some particular states of randomly selected molecules, the parameters of the new approach are computed to fit the phenomenological data to high accuracies. We also supply an analysis of the (pseudo-) potential implied in the new model, and compare it with the conventional model of the local potential that is applied in the explanation of the Dunham formula of energy spectra.