Electron correlations in molecules. I Bond orbital approximation

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

doi:10.1016/0301-0104(86)87035-5

Cited by 26 publications

(10 citation statements)

References 45 publications

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“…2 problem and has been reported previously [21] for two electrons in a two-center arrangement. For densities fii + 1.0 and 1D materials it corresponds to a reliable interpolation based on the bond orbital (BO) approximation [6]. The quality of the BO approximation has been demonstrated by comparing the present numerical results with data derived by Feynman path-integral quantum Monte-Carlo simulations [22].…”

Section: Theoretical Backgroundmentioning

confidence: 70%

“…The quality of the BO approximation has been demonstrated by comparing the present numerical results with data derived by Feynman path-integral quantum Monte-Carlo simulations [22]. For further theoretical details concerning the employed many-body procedure, see [6,17,211. In (3) Do is given in terms of the above occupancies Pi(2), P,(O) in the correlated ground state and the corresponding on-site density iii…”

Section: Theoretical Backgroundmentioning

confidence: 80%

“…We have adopted the local approach (LA) [6], a Gutzwiller-type method [8], in the so-called quasi-chemical approximation (QCA) to derive the correlated ground state \ y o ) for the studied low-dimensional CT salts. In the QCA the k-dependence of matrix elements is neglected, i.e.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…In two other theoretical contributions the Gutzwiller approach [S] for the evaluation of the correlated ground state has been used to derive a zero 191 and finite-temperature expression [lo] for x in the half-filled band case and the limit of weaker electronic correlations. In the present work we make use of a Gutzwiller-type of approach [6,8,111, which is valid for any strength of the electronic correlations and any band filling, on-site density f i i , respectively, to derive an expression for the magnetic susceptibility x in the metallic phase of quasi-one-dimensional organic CT salts. The validity of our model is demonstrated for the tetramethyltetraselenofulvalene salt (TMTSF),PF, and the 2,5dimethyl-dicyanoquinodiimine system (2,5-CH3-DCNQI),Ag.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic Susceptibilities of Low‐Dimensional Organic Donor–Acceptor Salts

Schulte¹,

Böhm²

1992

Physica Status Solidi (b)

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The magnetic susceptibility x of the low-dimensional organic charge-transfer salts TTF-TCNQ, (TMTSF),PF,, and (2,5-CH3-DCNQI),Ag is studied by a theoretical model which takes into account the X-enhancement due to electronic correlations as well as volume effects of the lattice as a function of temperature. Experimental data are reproduced both under constant pressure and constant volume conditions. The suggested approach reproduces the absolute values of x and the corresponding temperature gradient. The theoretical expressions are valid for any band filling and correlation strength.Die magnetische Suszeptibilitat x der niederdimensionalen Charge-Transfer-Salze TTF-TCNQ, (TMTSF),PF, und (2,5-CH3-DCNQI),Ag wird mit einem theoretischen Modell untersucht, bei dem sowohl die Erhohung von x durch elektronische Korrelationen als auch Volumeneffekte des Gitters (i.e. thermische Ausdehnung) als Funktion der Temperatur berucksichtigt werden. Experimentelle Daten, die entweder unter konstantem Druck oder konstantem Volumen gemessen worden sind, werden mit guter Genauigkeit wiedergegeben. Das vorgeschlagene theoretische Modell reproduziert sowohl die absoluten 1-Werte als auch den Temperaturverlauf der Suszeptibilitat. Die theoretischen Formeln gelten fur jede Bandbesetzung und Starke der elektronischen Korrelation.

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Section: Theoretical Backgroundmentioning

confidence: 70%

Section: Theoretical Backgroundmentioning

confidence: 80%

Section: Theoretical Backgroundmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Magnetic Susceptibilities of Low‐Dimensional Organic Donor–Acceptor Salts

Schulte¹,

Böhm²

1992

Physica Status Solidi (b)

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“…1 nearest neighbor octahedral places; 2,3, and 4 second, third, and fourth nearest neighbor octahedral places, respectively. The upper curve ( 0 ) is based on the mean-field approximation while electronic correlations in the H, subsystem (inter-and intra-atomic correlation) are considered in the lower one (a) 12 nearest neighboring octahedral places by a circle. The interatomic separation between the H atoms is here 0.249 nm.…”

Section: Resultsmentioning

confidence: 99%

H₂ Dissociation in Nickel. A Cluster Model

Vargas

Kronmüller

Böhm

1987

Physica Status Solidi (b)

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Dedicated t o Prof. Dr. A. SEECER on the occasion of his 60th birthday A cluster formed by 38 Ni atoms and two H atoms is studied by a semiempirical Hartree-Fock (HF) self-consistent-field (SCF) variant based on the INDO (intermediate neglect of differential overlap) approximation. The energy of the system is analyzed as a function of the spatial localization of t h e two H atoms. The energy minimum in the considered part of the singlet-type potential surface corresponds t o a spatial arrangement where the H atoms occupy nearest-neighbor oetahedral sites in the f.c.c. Ni-lattice (d(H-H) = 0.249 nm). This configuration is w l eV below anotlier local minimum which is associated to a "H2" molecule (d(H-H) = 0.085 nm) in the host system. The H atoms in the Ni-lattice can be characterized as overscreened protons. Ein Cluster von 38 Ni-Atomen und 2 H-Atomen wird mit einem semiempirischen Hartree-Fock (HE')-SCF-Verfahren auf der Basis einer INDO (intermediate neglect of differential overlap)-Naherung untersucht. Die Energie des Systems wird als Funktion der riiumlichen Lokalisierung der beiden H-Atome analysiert. Das Energieminimum in dem beriicksichtigten Teil der ,,Singlet"-Energie-Hyperflache wird fur eine Anordnung gefunden, in der die H-Atome auf benachbarten Okt~ederplatzen des kubiseh-flachenzentrierten Ni-Gitters lokalisiert sind (d(H-H) = 0,249 nm). Diese Anordnung ist zz 1 eV stebiler als ein zweites lokales Minimum, das einem ,,H,-Molekul" im Wirtsmetall entspricht (d(H-H) = 0,085 nm). Die H-Atome im Ni-Gitter verhalten sich wie "uberabgeschirmt.e" Protonen. l) Heisenbergstr. 1, D-7000 Stuttgart 80, FRG. 2, Petersenstr. 20, D-6100 Darmstadt, FRG. s, Permanent address: Physics Department, USACH, Santiago-2, Chile. 20 pliyniea (b) l44/l

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Charge fluctuations and correlation strength in chemical bonds: First-row homonuclear diatomic molecules

Yu¹,

Dolg²,

Fulde³

et al. 1998

Int. J. Quant. Chem.

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ABSTRACT:We investigate, by means of ab initio calculations, the strength of electron correlations within covalent bonds: the first-row homonuclear diatomics serve as test cases. As an appropriate measure of the correlation strength, we introduce the reduction of the mean-square deviations of the electronic charges in localized orbitals forming a bond. A recently developed population analysis in terms of local operators derived from localized molecular orbitals is thereby used. The correlation-strength parameter depends only weakly on dynamical correlations as test calculations demonstrate. Therefore, the full-valence complete active space self-consistent field Ž . CASSCF approximation is applied in order to study the changes in the correlation strength with changing bond length for different types of bonds. A number of simple rules emerge from this discussion. In addition, we show that charge fluctuations are not only a reliable measure of intrabond correlation effects, but also can be used to monitor intraatomic quasi-degeneracy effects as well as the interdependence within multiple bonds.

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Electron correlations in molecules. I Bond orbital approximation

Cited by 26 publications

References 45 publications

Magnetic Susceptibilities of Low‐Dimensional Organic Donor–Acceptor Salts

Magnetic Susceptibilities of Low‐Dimensional Organic Donor–Acceptor Salts

H₂ Dissociation in Nickel. A Cluster Model

Charge fluctuations and correlation strength in chemical bonds: First-row homonuclear diatomic molecules

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Electron correlations in molecules. I Bond orbital approximation

Cited by 26 publications

References 45 publications

Magnetic Susceptibilities of Low‐Dimensional Organic Donor–Acceptor Salts

Magnetic Susceptibilities of Low‐Dimensional Organic Donor–Acceptor Salts

H2 Dissociation in Nickel. A Cluster Model

Charge fluctuations and correlation strength in chemical bonds: First-row homonuclear diatomic molecules

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Product

Resources

About

H₂ Dissociation in Nickel. A Cluster Model