Quantum statistical analysis of superconductivity, fractional quantum Hall effect, and aromaticity

Bhm, Michael C.; Saal, Christoph

doi:10.1002/1097-461x(2000)79:3<125::aid-qua1>3.0.co;2-1

Cited by 11 publications

(32 citation statements)

References 95 publications

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“…Model calculations on small clusters have shown that Cooper pair formation can be driven by an attenuation of the destabilizing influence of Pauli antisymmetry constraints. In the T = 0 K studies on a direct pairing 8, 9, as well as in recent quantum Monte Carlo (QMC) simulations by the present authors 57–59, it has been demonstrated that many‐electron calculations in a basis of atomic occupation numbers render possible a physically useful fragmentation of the overall constraints acting on quantum particles. On this basis, they decompose into an on‐site and an intersite constraint.…”

Section: Introductionmentioning

confidence: 76%

“…The widely used electron–phonon (el–ph) formalism of Bardeen, Cooper, and Schrieffer (BCS) was developed more than four decades ago 3, 5–7. In the present finite‐temperature study, we discuss a direct, i.e., first‐order, pairing interaction that does not necessarily involve second‐order parameters, such as the el–ph coupling or magnetic interactions submitted by spin degrees of freedom 8, 9. The theoretical background of the first‐order interaction suggested is outlined below.…”

Section: Introductionmentioning

confidence: 99%

“…The conceptual deficits of pairing theories based on bare el–ph coupling have been described in the literature 1, 2. They have led to the development of alternative pairing mechanisms 8, 9, 34–47. In comparison with the dominating number of BCS studies, non‐BCS theories and applications are in the minority.…”

Section: Introductionmentioning

confidence: 99%

“…Other approaches have suggested interactions under exclusion of the el–ph coupling. Details can be found in the literature 8, 9, 34–47.…”

Section: Introductionmentioning

confidence: 99%

“…In recent zero‐temperature studies by one of the present authors (M.C.B.) 8, 9, a direct superconducting pairing has been introduced. The attractive interaction in this approach has been defined only by ground‐state parameters of H el .…”

Section: Introductionmentioning

confidence: 99%

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Steam methane reforming in a Ni/Al₂O₃ catalyst: Kinetics and diffusional limitations in extrudates

2009

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The true kinetics of methane steam reforming was measured in powder of Ni/Al 2 O 3 catalyst ("Octolyst 1001" from Degussa) at different temperatures (733-890 K) for several operating conditions. New reaction rate constants were determined for this catalyst. The observed reaction rate was measured on catalyst extrudates to determine diffusion effects within the porous structure of the particle. A non-isothermal model with diffusion was used to determine effectiveness factors for each reaction. The objective was to measure all necessary data to model the performance of the catalyst in a Sorption Enhanced Reaction Process (SERP) for H 2 production with in situ CO 2 capture.On a mesuré la cinétique réelle du reformageà la vapeur de méthane sur un catalyseur Ni/Al 2 O 3 sous forme de poudre (« Octolyst 1001 » de Degussa)à différentes températures (733-890 K) dans plusieurs conditions d'exploitation. De nouvelles constantes de vitesse de réaction ontété déterminées pour ce catalyseur. On a mesuré la vitesse de réaction observée sur des extrudats de catalyseur pour déterminer les effets de diffusioǹ a l'intérieur de la structure poreuse de la particule. On a utilisé un modèle non isothermique avec diffusion pour déterminer les facteurs d'efficacité de chaque réaction. L'objectif consistaità mesurer toutes les données nécessaires pour modéliser la performance du catalyseur dans un procédé de réaction améliorée de sorption pour la production de H 2 avec captage in-situ de CO 2 .

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Section: Introductionmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Other approaches have suggested interactions under exclusion of the el–ph coupling. Details can be found in the literature 8, 9, 34–47.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Steam methane reforming in a Ni/Al₂O₃ catalyst: Kinetics and diffusional limitations in extrudates

2009

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Cyclobutane—Physical Properties and Theoretical Studies

Wiberg

2009

Patai's Chemistry of Functional Groups

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Introduction Cycloalkane Structures and Bonding Bond Strengths Energies of Cycloalkanes NMR Spectra of Cycloalkanes Cyclopropyl and Cyclobutyl Cations Interaction of Cyclopropane and Cyclobutane Rings with Electron‐Deficient Centers Protonated Cyclopropanes and Cyclobutanes Thermal Formation of Cyclobutanes by Cycloaddition and Thermal Cleavage Antiaromaticity in Cyclobutadiene Summary

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Superconducting first‐order pairing: Finite‐temperature simulations

Böhm

Schulte

2004

Int J of Quantum Chemistry

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ABSTRACT:A recently developed first-order mechanism for superconducting pairing has been extended from T ϭ 0 K to finite temperatures. On the basis of quantum statistical considerations, we have suggested a direct pairing interaction that does not necessarily involve second-order elements, such as the electron-phonon coupling or specific magnetic interactions submitted by spin fluctuations. The driving force for the (energy-driven) first-order pairing is an attenuation of the destabilizing influence of the Pauli antisymmetry principle (PAP). Only the moves of unpaired fermions are controlled by the PAP, while the moves of superconducting Cooper pairs are not. The quantum statistics of Cooper pairs is of a mixed type, as it combines fermionic on-site and bosonic intersite properties. The strong correlation between the strength of PAP constraints and system topology in combination with the electron number has been discussed for some larger clusters. Detailed finite-temperature simulations on first-order pairing have been performed for four-center-four-electron clusters with different topologies. A canonical ensemble statistics has been employed to derive the electronic energy, the electronic configuration entropy, and the free energy of paired and unpaired states in thermal equilibrium. The simulations show that pairing can be caused by either the electronic energy or the electronic configuration entropy. The coexistence of two different sets of quantum particles in paired states (i.e., the Cooper pairs and the unpaired electrons) can lead to an enhanced configuration entropy. In this context, we discuss the possibility of an entropy-driven hightemperature superconductor emerging from a low-temperature unpaired state. The charge and spin degrees of freedom of the four-center-four-electron systems have been studied with the help of the charge and spin fluctuations. The spin fluctuations are helpful in judging the validity of pairing theories based on magnetic interactions. The charge fluctuations are a measure for the carrier delocalization in unpaired and paired states. The well-known proximity between Jahn-Teller activity and superconductivity is analyzed in the zero-temperature limit. It is demonstrated that both processes compete in their ability to reduce PAP constraints. All theoretical results have been derived within the framework of the simple Hubbard Hamiltonian.

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Quantum statistical analysis of superconductivity, fractional quantum Hall effect, and aromaticity

Cited by 11 publications

References 95 publications

Steam methane reforming in a Ni/Al₂O₃ catalyst: Kinetics and diffusional limitations in extrudates

Steam methane reforming in a Ni/Al₂O₃ catalyst: Kinetics and diffusional limitations in extrudates

Cyclobutane—Physical Properties and Theoretical Studies

Superconducting first‐order pairing: Finite‐temperature simulations

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Quantum statistical analysis of superconductivity, fractional quantum Hall effect, and aromaticity

Cited by 11 publications

References 95 publications

Steam methane reforming in a Ni/Al2O3 catalyst: Kinetics and diffusional limitations in extrudates

Steam methane reforming in a Ni/Al2O3 catalyst: Kinetics and diffusional limitations in extrudates

Cyclobutane—Physical Properties and Theoretical Studies

Superconducting first‐order pairing: Finite‐temperature simulations

Contact Info

Product

Resources

About

Steam methane reforming in a Ni/Al₂O₃ catalyst: Kinetics and diffusional limitations in extrudates

Steam methane reforming in a Ni/Al₂O₃ catalyst: Kinetics and diffusional limitations in extrudates