Attraction between like-charged walls: Short-ranged simulations using local molecular field theory

Effective attraction between like-charged walls mediated by counterions is studied using local molecular field (LMF) theory. Monte Carlo simulations of the "mimic system" given by LMF theory, with short-ranged "Coulomb core" interactions in an effective single particle potential incorporating a mean-field average of the long-ranged Coulomb interactions, provide a direct test of the theory, and are in excellent agreement with more complex simulations of the full Coulomb system by Moreira and Netz [Eur. Phys. J. E 8, 33 (2002)]. A simple, generally applicable criterion to determine the consistency parameter sigma(min) needed for accurate use of the LMF theory is presented.     

Equivalence between non-localizable and local fields

We discuss the nature of non-localisable fields constructed as certain limits of sequences of local fields. For sequences for which the corresponding Wightman functions converge we construct a PCT operator; if the sequences converge strongly in a given Hilbert space then a scattering theory can be constructed for the non-localisable limit field. Such fields are shown to have the sameS-operator as any local field which has the defining sequence of local fields in its Borchers class, and has the same in field. We give non-trivial examples of this equivalence between local and non-localisable fields.     

Effects of local fields on spontaneous emission in dielectric media

The local-field renormalization of the spontaneous emission rate in a dielectric is explicitly obtained from a fully microscopic quantum-electrodynamical, many-body derivation of Langevin-Bloch operator equations for two-level atoms embedded in an absorptive and dispersive, linear dielectric host. We find that the dielectric local-field enhancement of the spontaneous emission rate is smaller than indicated by previous studies.     

A molecular theory of the dielectric permittivity of a nematic liquid crystal

We present a theory of the dielectric permittivity in which the intermolecular dipole-dipole correlations are treated explicitly. The results for the static permittivity agree with those which have previously been obtained by continuum calculations. The frequency dependence of the permittivity is related to two relaxation times which contain the effects of only short range intermolecular correlations. Approximate relationships are derived between these times and independently measurable properties.     

Microscopic theory of surface dielectric response in a local representation

We give a formulation of surface dielectric response in a local LCAO or Wannier representation. It is shown that this representation allows for a practical solution of the response integral equation and thus makes possible an explicit and self-consistent calculation of the nonlocal RPA response function ?^-1. The formulation takes into account lattice potential effects and is therefore particularly suited for investigations of surface dielectric response and screening in transition metals, semiconductors and insulators. We present model calculations of charge densities induced in a metal thin film by localized perturbations in the surface region. It is demonstrated that “surface effects”, resulting from differences in the effective atomic potential for different layers, must be included in calculations of surface response in systems with tightly bound electrons.     

基于紧密耦合理论的3端分子桥的传导特性

利用基于紧密耦合理论的格林函数方法，考虑到每一个碳原子的π轨道电子，对3苯环构成的纳米分子桥的量子传输特性进行了理论研究。得出了从分子桥的一个端点到另外两个端点的电子传输概率。 利用基于Fisher-Lee公式的流密度方法，在传输概率出现峰值的能量点E=±0.42, ±1.06 和±1.5处，计算了分子桥内部的电流分布。其数值结果用图形模拟表示出来。我们发现传输谱与入射电子能量相关，并且紧密地依赖与分子能级。其结果显示电子流分布完全符合Kirchhoff量子动量守恒定律。     

A method of analysis of distributions of local electric fields in composites

A method of prediction of distributions of local electric fields in composite media based on analysis of the tensor operators of the concentration of intensity and induction is proposed. Both general expressions and the relations for calculating these operators are obtained in various approximations. The analytical expressions are presented for the operators of the concentration of electric fields in various types of inhomogeneous structures obtained in the generalized singular approximation.     

宏观分子自组装:一条架在分子和结构体之间的桥梁

文章介绍了一种新的分子自组装现象 :宏观分子自组装 .由一种新型的两亲性超支化多臂共聚物在丙酮中直接自组装形成厘米长度、毫米直径的宏观多壁螺旋管 .并对宏观管子的精细结构、性能进行了详细描述 ,同时阐述了宏观分子自组装机理 .宏观分子自组装现象的发现将分子自组装的研究领域推进到了宏观尺度范围 .     

The water molecule and its interactions: the interaction between theory, modelling, and experiment

Understanding the behaviour of water at the molecular level requires a quantitative understanding of the water molecule and its interactions. Although many current empirical potential functions are able to reproduce some of the known behaviour, our understanding of the water molecule and its interactions is not yet sufficient for our modelling to reproduce much of the subtleness of the water molecule's behaviour in both the pure liquid and in solution. Some recent experimental and theoretical developments are discussed that may lead to an improvement in our understanding of the water molecule and its interactions in a range of environments and over a range of experimental conditions.     

A new damped least-squares method for the calculation of molecular force fields

A modified Gauss method for the calculation of molecular force fields from spectroscopic data is presented. Comparison with other methods shows that it is capable of overcoming many of the frequently occurring convergence problems in least-squares force field optimization. The method has been tested by calculating valence and Urey-Bradley force fields for formaldehyde. The results are in good agreement with other force field calculations on the same molecule.     

A quantum mechanical theory of local observables and local operations

Local operators are characterized mathematically by means of projection operators on the Banach space of bounded operators. The idea of microlocality, as opposed to macrolocality, is implemented into the theory so as to enable us to define operations that are strictly local. Necessary and sufficient conditions are investigated in order that the interaction of a local measurement instrument with a local quantum field is such a strictly local (or microlocal) operation. Application of the theory to quantum electrodynamics reveals that this theory violates microlocality as defined here. Implications which our theory may have on the issue of quantum nonlocality as studied in relation to the Bell inequalities are discussed.     

On the relations between quantum fields and local algebras of observables

It is shown that quantum fields which are relatively local to a given local algebra of observables can be recovered from this algebra.     

The theory of SERS on semiconductor and dielectric substrates

It is demonstrated that the reason for SERS on dielectric and semiconductor substrates is enhancement of the electric field in the regions of the tops of surface roughness with a very small radius or a very large curvature. The enhancement depends on the dielectric constant of the substrate and is stronger for a larger dielectric constant. It is indicated that the enhancement on dielectrics and semiconductors is weaker than on metals with the same modulus of the dielectric constant. The result obtained is confirmed by experimental data on the enhancement coefficients obtained for various semiconductor and dielectric substrates.     

A remark on asymptotic completeness of local fields

Assuming the existence of an asymptotically complete Wightman field with non-trivialS-matrix, we construct a local field such that the Haag-Ruelle scattering theory applied to this field leads to.     

The operator method for perturbations in the theory of infrared molecular spectra

The application of contact transformations of Hamiltonians with a degenerate zeroth approximation to an approximate separation of variables is studied. Unitary transformations are formed that interrelate various effective Hamiltonians by the method of contact transformations of Van Vleck, Jorgensen, Pedersen, Primas, ENRST and Soliverez with an accuracy up to 0(⁵). The relation between the contact transformations and the perturbation theory of Rayleigh-Schrödinger is studied, and it is shown that the intermediate denominators in effective Hamiltonians vanish in a nondegenerate case. A generalized variant is constructed of contact transformations and of transformation yielding an even effective Hamiltonian from which the results of the above methods in particular cases follow.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, No. 7, pp. 82–90, July, 1977.The authors would like to thank V. N. Bryukhanov and P. I. Gaev for useful discussions.