Anab initio investigation of Cu2Se and Cu4Se2

Summary Experimentally known copper selenium clusters show extraordinary geometrical features, especially short Cu-Cu distances. We report the first theoretical investigation of Cu₂Se and Cu₄Se₂. Various quantum chemical methods (SCF, MP2, CPF, CCSD, CCSD(T), LDF) are applied to determine the importance of dynamic electron correlation. We find that inclusion of correlation does not essentially change the electronic structure of the clusters but has a strong influence on geometries. To reduce the computational effort we apply effective core potentials (ECPs) in combination with small, but carefully optimized basis sets. The applicability of simple modellings of correlation energies for approximate inclusion of correlation effects in SCF geometry optimizations is tested.     

Redox properties of hydrogenated quinoline derivatives — inhibitors in oxidation processes of hydrocarbons

Half-wave potentials of the one-electron electrochemical oxidation (E _1/2 ^ox) of hydroquinolines with different degrees of heterocycle hydrogenization as well as containing substituents of various natures in the benzene ring and heterocycle have been measured. Linear correlations betweenE _1/2 ^ox and the values of the Hammett polar -constants form- andp-substituents in dihydroquinolines and related sulfur-containing dithiolthiones were established. The character of the variation ofE _1/2 ^ox in the series of hydroquinolines was found to correlate with the characteristic features of the inhibiting action of these compounds in the liquid-phase oxidation of various hydrocarbons. However, in contrast to phenolic antioxidants for hydroquinolines, there is no dependence of the retardation period onE _1/2 ^oxin the oxidation of hydrocarbons at temperatures higher than 100 °C.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 610–613, April, 1994.     

Constrained minima of nonlocal free energy functionals

We consider variational problems involving nonlocal free energy functionals that arise from Gibbs measures with Kac potentials and are related to the characterization of the optimal (i.e., typical) shape of an interface under given constraints on the magnetization profile.     

Surface tension in Ising systems with Kac potentials

We consider an Ising spin system with Kac potentials in a torus of ^d,d>-2, and fix the temperature below its Lebowitz-Penrose critical value. We prove that when the Kac scaling parameter vanishes, the log of the probability of an interface becomes proportional to its area and the surface tension, related to the proportionality constant, converges to the van der Waals surface tension. The results are based on the analysis of the rate functionals for Gibbsian large deviations and on the proof that they -converge to the perimeter functional of geometric measure theory (which extends the notion of area). Our considerations include nonsmooth interfaces, proving that the Gibbsian probability of an interface depends only on its area and not on its regularity.     

Convergence of distorted Brownian motions and singular Hamiltonians

We prove a convergence theorem for sequences of Diffusion Processes corresponding to Dirichlet Forms of the kind .We obtain convergence in total variation norm of the corresponding probability measures on the path space C(₊;^d) under hypotheses which, for example, are satisfied in the case of H _loc ¹ ( ^d )-convergence of the 's, but we can allow more singular situations as regards the approximating sequences. We use then these results to give a criterion of convergence for generalized Schrödinger operators in which the potential function should not necessarily exists as a measurable function. We obtain convergence not only in strong resolvent sense, but we also obtain convergence in the uniform operator topology up to sets of arbitrarily small Lebesgue measure. Applications to the problem of the approximation of ordinary Schrödinger operators by generalized ones corresponding to zero-range interactions are given.     

用于语音识别中的SOFM矢量量化方法

该文讨论了神经网络语音识别系统中的ＫｏｈｏｎｅｎＳＯＦＭ神经网络的矢量量化（ＶＱ）的原理与过程,着重解决了其在实际应用时的若干问题,包括网络大小,学习步幅函数以及矢量量化过程中的公平竞争学习的控制函数的选定。过讨论了基于听觉模型的声学特性的提取与处理,这与ＶＱ性能息息相关。系统应用的实验表明,该神经网络在语音识别系统中具有良好性能。     

Exactly solvable XY model of the spin Peierls transition

The exact solution of the problem of the ground state of theXY-spin system on a deformed chain is found. At finite magnetizationm it is characterized by the double periodic structure and has a finite-band spectrum of spin excitations. Atm 0 the phase transition from the incommensurate into the dimerized state is accompanied by the soliton lattice formation.     

The Antiepileptic Lamotrigine and Its Analogues: Comparative Theoretical Electronic Properties

Electronic properties of lamotrigine (LTG) and two analogues (A1 and A2) are compared through MOPAC-AM1 calculations. Two stable conformers of LTG are calculated to exist in agreement with X-ray crystallography. In the three compounds and the two conformers for each of them, the more favorable protonation sites are N₂ and N₄; these should then be the sites appropriate for interaction with a receptor, and group valence reinforces the supposition. The molecular electrostatic potentials show that a region between the two chlorine atoms in LTG could be the site for an electrostatic interaction with a corresponding site in the receptor. The fluorine atom in A1 would play an equivalent role. A simple model for LTG-receptor interaction is proposed.     

Influence of static and dynamical structural changes on ultrafast processes mediated by conical intersections

The technological needs imposed by the exponential miniaturization trend of conventional electronic devices has drawn attention towards the development of smaller and faster devices like ultrafast molecular switches. In recent years molecular switches emerge again in the focus of active and innovative research with state-of-the-art optical tools recording their dynamics in real time. Still many questions about the underlying microscopic mechanism are left open, including potential factors that effect the switching process in either way, improve or worsen it. Due to the complexity of such molecules it is difficult to obtain a global answer from experiment alone. On the other side molecular switches are generally too large for a complete quantum chemical and quantum dynamical calculation. In our group we therefore developed an ab initio based modular model to handle the laser induced quantum dynamics in molecular switches like fulgides. It enables us to study the effect of internal molecular coupling and of the molecular response to external fields. We can investigate the related wave packet dynamics, the switching efficiency and the controllability. Our results focus on the laser induced ring opening in fulgides, which equals one direction of the switching process. Presented are the influence of a conical intersection seam and of time-dependent potentials, mimicking the mean interaction with the environment. Furthermore the relation of controllability and the wave packet's momentum is studied and the influence of potential barriers on the switching dynamics is shown.     

Evaluation of Multicenter Electronic Attraction, Electric Field and Electric Field Gradient Integrals with Screened and Nonscreened Coulomb Potentials over Integer and Noninteger n Slater Orbitals

By the use of complete orthonormal sets of -exponential-type orbitals, where ( = 1, 0, –1, –2,...) the multicenter electronic attraction (EA), electric field (EF) and electric field gradient (EFG) integrals of nonscreened and Yukawa-like screened Coulomb potentials are expressed through the two-center overlap integrals with the same screening constants and the auxiliary functions introduced in our previous paper (I.I. Guseinov, J. Phys. B, 3 (1970) 1399). The recurrence relations for auxiliary functions are useful for the calculation of multicenter EA, EF and EFG integrals for arbitrary integer and noninteger values of principal quantum numbers, screening constants, and location of slater-type orbitals. The convergence of the series is tested by calculating concrete cases.