Dynamical Mean Field Theory DMFT

It is believed that electron correlation plays an important role with the anomalously high resistivity exhibited in marginal metals. Unfortunately, although the Mott-Hubbard model adequately explains behavior on the insulating side of the M-NM transition, on the metallic side, it does so only if the system is far from the transition. Electron dynamics of systems in which U is only slightly less than W (i.e. metallic systems close to the M-NM transition), are not well described by a simple itinerant or localized picture. The study of systems with almost localized electrons is still an area under intense investigation within the condensed matter physics community. A dynamical mean field theory (DMFT) has been developed for the Hubbard model, which enables one to describe both the insulating state and the metallic state, at least for weak correlation. 

FLAPW GGA study of the structure and optical properties of AgFe02 and CuFe02 has been carried out by Blaha s group. " Ogata has reviewed band models of Na cCo02. This solid has also been the subject of a study by the recently-developed dynamic mean field theory (DMFT). This study used VASP with an LDA functional, a value of U = 3 eV for Co and an on-site potential for Na. It was found that the Na potential was the key to explaining the stronger correlation for X = 0.7 than for x = 0.3. 

Besides wave-function based methods (HF, Cl, CC) or DFT there is a third eategory that became important recently, namely many-body physics, which can handle correlation effects on a different level. Traditionally such schemes were often based on parameters but now they can be combined with DFT results. For example one can start with an EDA calculation and transform the basis set from a Bloch-picture to a Wannier description (see for example [8]). In the latter the correlated electrons can be described by the dynamical mean field theory (DMFT) which can... 

In the last 15 years, the Dynamical Mean Field Theory (DMFT) has been developed to investigate the properties for strongly correlated materials. Using this technique, the thermopower has been calculated, in particular in the case of a triangular lattice. Starting from the Hubbard model, the thermopower can be written at low T, as ... 

The LDA-fU theory may be regarded as an approximate GW method [37]. The screened Coulomb and exchange parameters U and J are usually estimated in a supercell approximation [39]. However, there is some arbitrariness in the choice of the localized orbitals when performing the partitioning of the Hamiltonian. A further step in the improvement of LDA-I-U consists in adding dynamical effects — frequency dependence in H r,r u). This may be performed using a DMFT-type approach (DMFT= Dynamical Mean Field Theory) [40] as part of the so-called LDA-b-1- approaches [41]. 

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