A method of calculating electron correlations for large molecules involving C, N, and H atoms

Oleś, Andrzej M.; Pfirsch, F.; Fulde, Peter; Böhm, Michael

doi:10.1063/1.451857

Cited by 46 publications

(14 citation statements)

References 27 publications

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“…in titanium or vanadium oxides) are even stronger correlated than e g electrons in the RMnO 3 or RNiO 3 perovskites. This resembles the situation in molecular bonds in sp systems, with π bonds being always stronger correlated than σ bonds [17]. A second class of correlated insulators, so-called charge transfer insulators, arises when the oxygen states are within the gap between the two Hubbard subbands [18].…”

Section: Degrees Of Freedom In Transition Metal Oxidesmentioning

confidence: 99%

Charge and Orbital Order in Transition Metal Oxides

Oleś

2010

Acta Phys. Pol. A

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A short introduction to the complex phenomena encountered in transition metal oxides with either charge or orbital or joint charge-and-orbital order, usually accompanied by magnetic order, is presented. It is argued that all the types of above ordered phases in these oxides follow from strong Coulomb interactions as a result of certain compromise between competing instabilities towards various types of magnetic order and optimize the gain of kinetic energy in doped systems. This competition provides a natural explanation of the stripe order observed in doped cuprates, nickelates and manganites. In the undoped correlated insulators with orbital degrees of freedom the orbital order stabilizes particular types of anisotropic magnetic phases, and we contrast the case of decoupled (disentangled) spin and orbital degrees of freedom in the manganites with entangled spin-orbital states which decide about certain rather exotic phenomena observed in the perovskite vanadates at finite temperature. Examples of successful concepts in the theoretical approaches to these complex systems are given and some open problems of current interest are indicated. Degrees of freedom in transition metal oxidesThe physical properties of transition metal oxides are driven by strong electron interactions [1]. It is due to strong local Coulomb interactions that these systems exhibit very interesting and quite diverse instabilities towards ordered magnetic phases when doping x or temperature T is varied -is some cases also with orbital order. These instabilities are observed, inter alia, in rapid changes of the transport properties at the metalinsulator phase transitions, or in the onset of superconductivity.One of the outstanding problems in modern condensed matter theory is the description of strongly correlated electrons in various systems. When local Coulomb interactions are strong, the usual methods used for calculating the electronic structure fail and have to be extended by the terms following from local interactions, either in the framework of the local density approximation (LDA) with Coulomb U , the so-called LDA+U method [2], or by the self-energy within the dynamical mean-field theory (DMFT) [3], in the LDA + DMFT approach [4]. This latter approach makes use of the local self-energy which becomes exact in the limit of infinite spatial dimension d = ∞ [5]. However, even these methods cannot overcome certain shortcomings of the effective one-particle theory which justifies modelling of the transition metal * Dedicated to the memory of the late Professor Jan Stankowski. * * e-mail: a.m.oles@fkf.mpg.de oxides with Hamiltonians of the Hubbard type, and looking for solutions with methods of quantum many-body theory. The advantage of recent rapid progress in the electronic structure calculations is that such models can use realistic parameters nowadays, which follow from the electronic structure calculations for a given system. Although the field of strongly correlated electronic systems is very rich, we shall concentrate here on the phe...

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Section: Degrees Of Freedom In Transition Metal Oxidesmentioning

confidence: 99%

Charge and Orbital Order in Transition Metal Oxides

Oleś

2010

Acta Phys. Pol. A

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“…It is known from the pioneering work of Pauling, Mulliken, Coulson and other authors [8,9,10], that bond order and molecular bond length are strongly correlated. In this sense our work is somewhat related to the work of Fulde et al [11,12], where an analytical model of molecular correlation energies based on bond lengths was proposed.…”

Section: Introductionmentioning

confidence: 89%

Bond-order correlation energies for small Si-containing molecules compared withab initioresults from low-order Møller–Plesset perturbation theory

et al. 2006

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The present study of small molecules containing silicon has been motivated by (a) the considerable interest being shown currently in the kinetics and reactivity of such molecules, and (b) the biotechnological potential of silicon-derivate surfaces as substrates in the adsorption of, for instance, amino acids and proteins. Therefore, we have studied by (i) a semi-empirical approach and (ii) an ab initio procedure employing low-order Møller-Plesset perturbation theory, the molecular correlation energies of some neutral closed and open shell silicon-containing molecules in the series SiX n Y m . Procedure (i) is shown to have particular merit for the correlation of the ionic members studied in the above series, while the ab initio procedures employed come into their own for neutral species.

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“…These parameters are fixed as follows for the Cu-O plane. Our previous studies [15] have demonstrated that atomic values of the Coulomb interaction have to be used in order to obtain the correct interatomic correlation energies for bonds formed by s and p electrons. The same applies in principle to d electrons.…”

Section: Resultsmentioning

confidence: 99%

HOW STRONGLY ARE ELECTRONS CORRELATED IN THE HIGH-Tc SUPERCONDUCTING MATERIALS?

OLEĆ¹,

ZAANEN²,

FULDE³

1987

Proceedings of the Yamada Conference XVIII on Superconductivity in Highly Correlated Fermion Systems

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Electron correlations within CuO 2 layers, a common structural unit in La-Ba-Cu-O and Y-Ba-Cu-O systems, are studied by using a tight-binding model Hamiltonian. It is found that electron correlations are particularly strong within Cu(3dx2 y2) orbitals. They do not only considerably suppress charge fluctuations, but also change the electron densities. As a consequence~ the average number of holes at Cu sites increases and local moments are formed. Our results agree qualitatively with the experimentally observed magnetic moments in the antiferromagnetic phase and support the point of view that these systems are similar to valence fluctuating systems.

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A method of calculating electron correlations for large molecules involving C, N, and H atoms

Cited by 46 publications

References 27 publications

Charge and Orbital Order in Transition Metal Oxides

Charge and Orbital Order in Transition Metal Oxides

Bond-order correlation energies for small Si-containing molecules compared withab initioresults from low-order Møller–Plesset perturbation theory

HOW STRONGLY ARE ELECTRONS CORRELATED IN THE HIGH-Tc SUPERCONDUCTING MATERIALS?

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