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1.
K. Held D. Vollhardt 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):473-478
The importance of Hund's rule coupling for the stabilization of itinerant ferromagnetism is investigated within a two-band
Hubbard model. The magnetic phase diagram is calculated by finite-temperature quantum Monte-Carlo simulations within the dynamical
mean-field theory. Ferromagnetism is found in a broad range of electron fillings whereas antiferromagnetism exists only near
half filling. The possibility of orbital ordering at quarter filling is also analyzed.
Received: 26 February 1998 / Accepted: 17 April 1998 相似文献
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Dodecaynes 1a-d have been prepared via a convergent strategy that employs Sonogashira couplings as the carbon-carbon bond-forming tool. Due to the steric bulk of the DMTS groups, 1c adopts a nonplanar conformation, the dynamics of which have been probed by VT-NMR. The cobalt-catalyzed isomerization of 1a,b produced the new conjugated phenylenes 2a,b and 3a,b, respectively. [structure: see text] 相似文献
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N. Nandi D. Vollhardt R. Rudert 《Colloids and surfaces. A, Physicochemical and engineering aspects》2004,250(1-3):279-287
In the present work, the pair potential of enantiomeric N-palmitoyl aspartic acid amphiphile monolayer at the air/water interface is calculated based on an atomistic model. The molecular structure and partial charges are calculated using two semi empirical (PM3, AM1) and one empirical (Gasteiger and Marcili) methods. A distance-dependent dielectric function is used to represent the interfacial dielectric constant at the aqueous subphase. The present study indicates that a pair of molecules have favorable interaction at specific ranges of mutual orientations. Other orientations are favorable but at larger separations. Favorable electrostatic interaction at a specific combination of orientation and short separations of the head groups significantly contribute to the total energy. The curvature of the domain boundary is suggested to be driven by the favorable arrangement which is dependent on the pair potential of molecules. The use of charges obtained by the PM3 and GM do not lead to a significant variation of the orientation-dependent features, while the AM1 predicts higher partial charges and interactions are stronger than the former two methods. However, orientation-dependent features remain the same. The variations in the LJ parameters and charges indicate that the conclusions made are insensitive to the choice of parameters. The mutual favorable interaction predicted by calculation agree with the handedness of curvature of domains. 相似文献
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D. Vollhardt 《Annalen der Physik》2012,524(1):1-19
Electronic correlations strongly influence the properties of matter. For example, they can induce a discontinuous transition from conducting to insulating behavior. In this paper basic terms of the physics of correlated electrons are explained. In particular, I describe some of the steps that led to the formulation of a comprehensive, non‐perturbative many‐body approach to correlated quantum many‐body systems, the dynamical mean‐field theory (DMFT). The DMFT becomes exact in the limit of high lattice dimensions (d → ∞) and allows one to go beyond the investigation of simple correlation models and thereby better understand, and even predict, the properties of electronically correlated materials. 相似文献
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