[PDF] New Concepts In Electron Correlation With Application To Extended Systems eBook

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Publisher :
Page : 10 pages
File Size : 20,64 MB
Release : 1998
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ISBN :

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The objective of our work for ONR has been to develop and apply new, correlated electronic structure methods for infinite periodic systems. The methods of interest include many body perturbation theory (MBPT) and its infinite order coupled cluster generalizations and complementary density functional methods. Today we routinely do highly correlated studies of molecules (including making reliable predictions of structure, photoelectron, vibrational, and electronic spectra). The next frontier in electronic structure theory is the treatment (with the same level of confidence) of polymers, surfaces, and crystals, which are semiconductors or insulators and are collectively termed "extended systems." The current paradigm for molecules is SCF, MBPT(2), CCSD, CCSD(T), CCSDT, and full CI. Though convergence is not monotonic, such a sequence, augmented by experience and approximate error bars, typically offers purely ab inito, extrapolated solutions that are predictive. In contrast, no such paradigm exists for extended systems. Furthermore, there is no full CI so only high-level CC methods can offer reference results. The only methods currently available for extended systems are periodic Hartree Fock (i.e., SCF) and density functional theory (DFT), usually in the local density approximation (LDA). The former lacks the critical electron correlation effects responsible for so many of the interesting phenomena in solids, from band gaps to high Tc superconductivity, while the latter might introduce some correlation effects, but an unclear amount. In fact, the greatest weakness of DFT is that, unlike the above CC/MBPT paradigm, there is no way to systematically converge to the correct result.

Author : Alex C. Hewson
Publisher : Springer Science & Business Media
Page : 364 pages
File Size : 16,29 MB
Release : 2012-12-06
Category : Science
ISBN : 9401002134

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The NATO sponsored Advanced Research Workshop on "Concepts in Electron Correlation" took place on the Croatian island of Hvar during the period from the 29th of September to the 3rd of October, 2002. The topic of electron correlation is a fundamental one in the field of condensed matter, and one that is being very actively studied both experimentally and theoretically at the present time. The manifestations of electron cor relation are diverse, and play an important role in systems ranging from high temperature superconductors, heavy fermions, manganite compounds with colossal magnetoresistance, transition metal compounds with metal insulator transitions, to mesoscopic systems and quantum dots. The aim of the workshop was to provide an opportunity for a dialogue between exper imentalists and theoreticians to assess the current state of understanding, and to set an agenda for future work. There was also a follow-up workshop on the same topic where the presentations included more background and introductory material for younger researchers in the field. The papers presented in these proceedings clearly demonstrate the di versity of current research on electron correlation. They show that real progress is being made in characterising systems experimentally and in developing theoretical approaches for a quantitative comparison with ex periment. The more one learns, however, the more there is to understand, and many of the contributions help to map out the territory which has yet to be explored. We hope that the articles in this volume will be a stimulus for such future work.

Author : Jamal Berakdar
Publisher : John Wiley & Sons
Page : 205 pages
File Size : 20,99 MB
Release : 2008-07-11
Category : Science
ISBN : 3527618538

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An up-to-date selection of applications of correlation spectroscopy, in particular as far as the mapping of properties of correlated many-body systems is concerned. The book starts with a qualitative analysis of the outcome of the two-particle correlation spectroscopy of localized and delocalized electronic systems as they occur in atoms and solids. The second chapter addresses how spin-dependent interactions can be imaged by means of correlation spectroscopy, both in spin-polarized and extended systems. A further chapter discusses possible pathways for the production of interacting two-particle continuum states. After presenting some established ways of quantifying electronic correlations and pointing out the relationship to correlation spectroscopy, the author addresses in a separate chapter the electron-electron interaction in extended systems, and illustrates the ideas by some applications to fullerenes and metal clusters. The last two chapters are devoted to the investigation of the potential of two-particle spectroscopy in studying ordered surfaces and disordered samples. Throughout the book the material is analyzed using rather qualitative arguments, and the results of more sophisticated theories serve the purpose of endorsing the suggested physical scenarios. The foundations of some of these theories have been presented in a corresponding volume entitled "Concepts of Highly Excited Electronic Systems" (3-527-40335-3).

Author :
Publisher : Academic Press
Page : 354 pages
File Size : 43,50 MB
Release : 2021-09-28
Category : Science
ISBN : 0128235470

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Advances in Quantum Chemistry presents surveys of current topics in this rapidly developing field one that has emerged at the cross section of the historically established areas of mathematics, physics, chemistry, and biology. It features detailed reviews written by leading international researchers. In this volume the readers are presented with an exciting combination of themes. Presents surveys of current topics in this rapidly-developing field that has emerged at the cross section of the historically established areas of mathematics, physics, chemistry and biology Features detailed reviews written by leading international researchers

Author : Jamal Berakdar
Publisher : Wiley-VCH
Page : 0 pages
File Size : 16,57 MB
Release : 2006-03-31
Category : Science
ISBN : 9783527404124

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Knowledge of the excitation characteristics of matter is decisive for the descriptions of a variety of dynamical processes, which are of significant technological interest. E.g. transport properties and the optical response are controlled by the excitation spectrum. This self-contained work is a coherent presentation of the quantum theory of correlated few-particle excitations in electronic systems. It begins with a compact resume of the quantum mechanics of single particle excitations. Particular emphasis is put on Green function methods, which offer a natural tool to unravel the relations between the physics of small and large electronic systems. The book contains explicit expressions for the Coulomb Green function of two charge particles and a generalization to three-body systems. Techniques for the many-body Green function of finite systems are introduced and some explicit calculations of the Green functions are given. Concrete examples are provided and the theories are contrasted with experimental data, when available. A complimentary volume presents an up-to-date selection of applications of the developed concepts and a comparison with available experiments is made

Author : Peter Fulde
Publisher : Springer Science & Business Media
Page : 492 pages
File Size : 48,42 MB
Release : 2012-12-06
Category : Science
ISBN : 3642578098

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Dieser Titel verbindet die Festkörpertheorie mit der Quantenchemie. Neue Konzepte der Vielteilchen-Verarbeitung und Korrelations-Effekte, normale quantenchemische Verfahren mit Projektionstechniken, Greensche Funktionen und Monte-Carlo-Methoden werden erarbeitet. Anwendungsbereiche der Molekültheorie, von Halbleitern, supraleitender high-Tc-Materialien, etc., werden vorgestellt.

Author : Motoi Tobita
Publisher :
Page : pages
File Size : 16,38 MB
Release : 2002
Category :
ISBN :

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ABSTRACT: This dissertation is focused on the development of highly accurate electron-correlation methods for one- and two-dimensional periodic systems. For one-dimensional systems, atomic-orbital based many-body perturbation theory and coupled cluster theory are developed and applied to polyacetylene and lithium-hydride model chain. Use of atomic orbitals instead of conventional crystalline (molecular) orbitals enables us to control runtime and accuracy of the calculation. The gain in the atomic-orbital based coupled cluster method originates from the locality and sparsity of matrices needed in the framework of the theory. Provided, efficient sparse matrix-matrix multiplication routines, we obtain good estimates of the correlation energy much faster than the conventional method for large systems. 90 percent of the correlation energy can be recovered very quickly, and 2 to 3 digit accuracy can be obtained for polymers with relatively simple unit cells such as polyacetylene. The formalism behind the atomic-orbital based coupled cluster theory is applicable for both large molecular systems and periodic systems. Formal aspects of the atomic-orbital based coupled cluster theory are discussed and correspondence between the atomic-orbital based framework and crystalline (molecular) orbital based framework are shown. Two-dimensional code development is based on Hartree-Fock and density functional theories due to the fact that coupled-cluster theory is too costly. Efficient inclusion of the Coulomb effects by the fast multipole method and analytical gradient techniques are the core elements that contribute robustness and computational efficiency for two-dimensional systems. The fast multipole method is an algorithm to include the long-range Coulomb effects for uniform systems with linear-scaling costs for molecular systems and with logarithmic scaling for infinite periodic systems. The analytical gradient technique is a powerful tool when optimized geometries or vibrational frequencies are computed. If optimum geometries or vibrational frequencies are required, then analytical gradients are for all practical purposes, a necessity.

Author : Naoto Nagaosa
Publisher : Springer Science & Business Media
Page : 188 pages
File Size : 43,46 MB
Release : 1999-09-20
Category : Science
ISBN : 9783540659815

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In this book the author extends the concepts introduced in his Quantum Field Theory in Condensed Matter Physics to situations in which the strong electronic correlations are crucial for the understanding of the observed phenomena. Starting from a model field theory to illustrate the basic ideas, more complex systems are analyzed in turn. A special chapter is devoted to the description of antiferromagnets, doped Mott insulators, and quantum Hall liquids from the point of view of gauge theory.

Author : Peter Fulde
Publisher : World Scientific
Page : 550 pages
File Size : 25,81 MB
Release : 2012-08-08
Category : Science
ISBN : 9814397229

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An understanding of the effects of electronic correlations in quantum systems is one of the most challenging problems in physics, partly due to the relevance in modern high technology. Yet there exist hardly any books on the subject which try to give a comprehensive overview on the field covering insulators, semiconductors, as well as metals. The present book tries to fill that gap.It intends to provide graduate students and researchers a comprehensive survey of electron correlations, weak and strong, in insulators, semiconductors and metals. This topic is a central one in condensed matter and beyond that in theoretical physics. The reader will have a better understanding of the great progress which has been made in the field over the past few decades.

Author : Jozef T. Devreese
Publisher : Springer Science & Business Media
Page : 440 pages
File Size : 31,98 MB
Release : 2012-12-06
Category : Science
ISBN : 1461334977

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From July 20 till 31, 1981, the Advanced Study Institute on "Electron Correlations in Solids, Molecules and Atoms", sponsored by NATO, was held at the University of Antwerpen (U.I.A.), in the Conference Center Corsendonk. In the last few years, the problem of many-electron correlations has gained renewed attention, due to recent experimental and theoretic al developments. From the theoretical point of view, more sophisticated treatments of the homogeneous electron gas model evolved, including dynamical aspects of the electron correlation in the dielectric response. Furthermore, the homogeneous electron gas, which served as a model for simple metals, was extended to include spin- and charge-density waves and phasons. The concept of elementary excitations too was introduced not only in perfectly ordered metallic crystals, but also in magnetic alloys, in liquid metals and alloys, in semiconductors, and even in molecules and atoms. Fairly accurate quantitative calculations of these effects recently became possible, ranging from plasmon frequencies in atoms, over dielectric response of semiconduc tors and resistivity in magnetic alloys to electron-hole liquids and their phase separation. The recent technological evolution allowed for more accurate measurements in previously unaccessible domains, e.g. X-ray scatter ing and fast electron energy loss at large wavevector. Moreover, these new developments opened new perspectives in physics, accompany ing or even introducing the new concepts which also evolved in the theory.