We propose a computational scheme for the ab initio calculation of Wannier functions (WFs) for correlated electronic materials. The full-orbital HamiltonianĤ is projected into the WF subspace defined by the physically most relevant partially filled bands. The HamiltonianĤ W F obtained in this way, with interaction parameters calculated by constrained LDA for the Wannier orbitals, is used as an ab initio setup of the correlation problem, which can then be solved by many-body techniques, e.g., dynamical mean-field theory (DMFT). In such calculations the self-energy operator Σ(ε) is defined in WF basis which then can be converted back into the full-orbital Hilbert space to compute the full-orbital interacting Green function G(r, r ′ , ε). Using G(r, r ′ , ε) one can evaluate the charge density, modified by correlations, together with a new set of WFs, thus defining a fully selfconsistent scheme. The Green function can also be used for the calculation of spectral, magnetic and electronic properties of the system. Here we report the results obtained with this method for SrVO 3 and V 2 O 3 . Comparisons are made with previous results obtained by the LDA+DMFT approach where the LDA DOS was used as input, and with new bulk-sensitive experimental spectra.

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A hybrid scheme for the electronic structure calculations of strongly correlated electron systems is proposed. The ab initio local density approximation calculation is used to construct the Wannier functions and obtain single electron and Coulomb parameters of the multiband Hubbard-type model. In strong correlation regime the electronic structure within multiband Hubbard model is calculated by the generalized tight-binding method, which combines the exact diagonalization of the model Hamiltonian for a small cluster ͑unit cell͒ with perturbation treatment of the intercluster hopping and interactions. For undoped La 2 CuO 4 and Nd 2 CuO 4 this scheme results in charge transfer insulators with correct values of gaps and dispersions of bands in agreement with the angle-resolved photoemission data.

In the framework of the LDA+U approximation we propose the direct way of calculation of crystalfield excitation energy and apply it to La and Y titanates. The method developed can be useful for comparison with the results of spectroscopic measurements because it takes into account fast relaxations of electronic system. For titanates these relaxation processes reduce the value of crystalfield splitting by ∼ 30% as compared with the difference of LDA one electron energies. However, the crystal-field excitation energy in these systems is still large enough to make an orbital liquid formation rather unlikely and experimentally observed isotropic magnetism remains unexplained.PACS numbers: 71.15.-m, 71.20.-b, 71.30.+h

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The importance of electronic correlation effects in the layered perovskite Sr2RuO4 is evidenced. To this end we use state-of-the-art LDA+DMFT (Local Density Approximation + Dynamical MeanField Theory) in the basis of Wannier functions to compute spectral functions and the quasiparticle dispersion of Sr2RuO4. The spectra are found to be in good agreement with various spectroscopic experiments. We also calculate the k-dependence of the quasiparticle bands and compare the results with new angle resolved photoemission (ARPES) data. Two typical manifestations of strong Coulomb correlations are revealed: (i) the calculated quasiparticle mass enhancement of m * /m ≈ 2.5 agrees with various experimental results, and (ii) the satellite structure at about 3 eV binding energy observed in photoemission experiments is shown to be the lower Hubbard band. For these reasons Sr2RuO4 is identified as a strongly correlated 4d electron material.

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In this Letter we report the first LDA+DMFT (method combining Local Density Approximation with Dynamical Mean-Field Theory) results of magnetic and spectral properties calculation for paramagnetic phases of FeO at ambient and high pressures (HP). At ambient pressure (AP) calculation gave FeO as a Mott insulator with Fe 3d-shell in high-spin state. Calculated spectral functions are in a good agreement with experimental PES and IPES data. Experimentally observed metal-insulator transition at high pressure is successfully reproduced in calculations. In contrast to MnO and Fe2O3 (d 5 configuration) where metal-insulator transition is accompanied by high-spin to low-spin transition, in FeO (d 6 configuration) average value of magnetic moment < µ 2 z > is nearly the same in the insulating phase at AP and metallic phase at HP in agreement with X-Ray spectroscopy data (Phys. Rev. Lett. 83, 4101 (1999)). The metal-insulator transition is orbital selective with only t2g orbitals demonstrating spectral function typical for strongly correlated metal (well pronounced Hubbard bands and narrow quasiparticle peak) while eg states remain insulating.