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Coulomb Correlation (coulomb + correlation)
Selected AbstractsElectron correlation: The many-body problem at the heart of chemistryJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 8 2007David P. Tew Abstract The physical interactions among electrons and nuclei, responsible for the chemistry of atoms and molecules, is well described by quantum mechanics and chemistry is therefore fully described by the solutions of the Schrödinger equation. In all but the simplest systems we must be content with approximate solutions, the principal difficulty being the treatment of the correlation between the motions of the many electrons, arising from their mutual repulsion. This article aims to provide a clear understanding of the physical concept of electron correlation and the modern methods used for its approximation. Using helium as a simple case study and beginning with an uncorrelated orbital picture of electronic motion, we first introduce Fermi correlation, arising from the symmetry requirements of the exact wave function, and then consider the Coulomb correlation arising from the mutual Coulomb repulsion between the electrons. Finally, we briefly discuss the general treatment of electron correlation in modern electronic-structure theory, focussing on the Hartree-Fock and coupled-cluster methods and addressing static and dynamical Coulomb correlation. © 2007 Wiley Periodicals, Inc. J Comput Chem 28: 1307,1320, 2007 [source] Linear excitonic absorption under an external electric field in quantum dot moleculesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2007M. Bedoya Abstract A study of the excitonic states in artificial molecules set up of two vertically coupled double quantum dots is presented. The electron and hole eigenstates are calculated for the quantum dot molecule. In particular, the coupling effect of the barrier and the consequent tunneling is analyzed following the evolution of the absorption spectra as function of the distance between the two dots. On the other hand, the role of the Coulomb correlation between the confined particles is also studied. We present results of relevant interactions in these systems and discuss how the optical properties of double quantum dots are affected by the interdot coupling, by the geometry of the dots and by an applied electric field. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Optical properties of correlated materials , Or why intelligent windows may look dirty,PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 9 2009Jan M. Tomczak Abstract Materials with strong electronic Coulomb correlations play an increasing role in modern materials applications. "Thermochromic" systems, which exhibit thermally induced changes in their optical response, provide a particularly interesting case. The optical switching associated with the metal,insulator transition of vanadium dioxide (VO2), for example, has been proposed for use in numerous applications, ranging from anti-laser shields to "intelligent" windows, which selectively filter radiative heat in hot weather conditions. Are present-day electronic structure techniques able to describe, or , eventually even predict , such a kind of behavior? How far are we from materials design using correlated oxides? These are the central questions we try to address in this article. We review recent attempts of calculating optical properties of correlated materials within dynamical mean field theory, and summarize results for VO2 obtained within a novel scheme aiming at particularly simple and efficient calculations of optical transition matrix elements within localized basis sets. Finally, by optimizing the geometry of "intelligent windows," we argue that this kind of technique can, in principle, be used to provide guidance for experiments, thus giving a rather optimistic answer to the above questions. [source] Particle,hole asymmetry in the scanning tunneling spectroscopy of the high temperature superconductorsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2007Anna Gorczyca Abstract There is still no consensus on the mechanism that is responsible for a particle,hole asymmetry observed in scanning tunneling spectroscopy of high-temperature superconductors. According to the most popular hypothesis this asymmetry results from strong Coulomb correlations in a nearly half-filled band. In the present paper we propose another mechanism that leads to such asymmetry. It originates from the coupling between the superconductor and the substrate that the system is deposed on. We show that this coupling gives rise to the particle,hole asymmetry only in the case of an anisotropic superconductivity. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||