The electronic structures and transport properties of a series of actinide mono carbides, mono nitrides and dioxides are studied systematically using a combination of density functional theory and dynamical mean field theory. The studied materials present different electronic correlation strength and degree of localization of 5f -electrons, where a metal-insulator boundary naturally lies within. In the spectral function of Mott-insulating uranium oxide, a resonance peak is observed in both theory and experiment and may be understood as a generalized Zhang-Rice state. We also investigate the interplay between electron-electron and electron-phonon interactions, both of which are responsible for the transport in the metallic compounds. Our findings allow us to gain insight in the roles played by different scattering mechanisms, and suggest how to improve their thermal conductivities.

We show that the electron-phonon coupling (EPC) in many materials can be significantly underestimated by the standard density functional theory (DFT) in the local density approximation (LDA) due to large non-local correlation effects. We present a simple yet efficient methodology to evaluate the realistic EPC going beyond LDA by using more advanced and accurate GW and screened hybrid functional DFT approaches. The corrections we propose explain the extraordinarily high superconducting temperatures that are observed in two distinct classes of compounds-the bismuthates and the transition metal chloronitrides, thus solving a thirty-year-old puzzle. Our work calls for the critically reevaluation of the EPC of certain phonon modes in many other materials such as cuprates and iron-based superconductors. The proposed methodology can be used to design new correlation-enhanced high temperature superconductors and other functional materials involving electron-phonon interaction.

We present the results of calculations for Pu and Am performed using an implementation of self-consistent relativistic GW method. The key feature of our scheme is to evaluate polarizability and self-energy in real space and Matsubara's time. We compare our GW results with the calculations using local density (LDA) and quasiparticle (QP) approximations and also with scalar-relativistic calculations. By comparing our calculated electronic structures with experimental data, we highlight the importance of both relativistic effects and effects of self-consistency in this GW calculation.

The band gaps of a few selected semiconductors/insulators are obtained from the self-consistent solution of the Hedin's equations. Two different schemes to include the vertex corrections are studied: (i) the vertex function of the first-order (in the screened interaction W ) is applied in both the polarizability P and the self-energy Σ, and (ii) the vertex function obtained from the BetheSalpeter equation is used in P whereas the vertex of the first-order is used in Σ. Both schemes show considerable improvement in the accuracy of the calculated band gaps as compared to the selfconsistent GW approach (scGW ) and to the self-consistent quasi-particle GW approach (QSGW ). To further distinguish between the performances of two vertex-corrected schemes one has to properly take into account the effect of the electron-phonon interaction on the calculated band gaps which appears to be of the same magnitude as the difference between schemes i) and ii).

We introduce a first principles approach to determine the strength of the electronic correlations based on the fully self consistent GW approximation. The approach provides a seamless interface with dynamical mean field theory, and gives good results for well studied correlated materials such as NiO. Applied to the recently discovered iron arsenide materials, it accounts for the noticeable correlation features observed in optics and photoemission while explaining the absence of visible satellites in X-ray absorption experiments and other high energy spectroscopies.Many metals, semiconductors, and insulators are well described by the "standard model" of solid state physics. In this picture the excitations are band electrons, and their dispersion can be computed quantitatively in perturbation theory starting from the density functional theory using the GW method [1]. When this standard model fails, we talk about strongly correlated electron systems. The presence of strong correlations is debated with each new material discovery, as for example in the context of the iron pnictide superconductors. On the experimental side, controversies arose because optical experiments revealed significant mass renormalizations [2-4] while Xray absorption, core level spectroscopies and resonant inelastic Xray scattering indicated the absence of satellite peaks [5,6], which are standard fingerprints of strong correlations. Photoemission studies indicate that the overall bandwidth is narrowed by a factor of two [7,8] but substantially larger mass renormalizations are present near the Fermi level [9]. Similar controversies arose within the first principles approaches to the treatment of correlations with some theoretical studies supporting the notion of weak correlations [10][11][12][13][14], while others advocate a more correlated picture [15][16][17][18]. To make progress on this issues one needs to develop fully ab initio tools for addressing the problem of determining the strength of correlations and test their predictions against experiments.In this letter we introduce a new first principles methodology for evaluating the strength of the correlations based on the self-consistent GW method. This approach has been shown to predict accurate total energy [19,20], and we expect to obtain reliable estimates for the interaction strength since this quantity can be thought as a second derivative of the total energy with respect to the occupation of the correlated orbitals. We test successfully the method on the well studied example of a correlated material NiO, and then we apply it to a prototypical iron pnictide BaFe 2 As 2 . We find that the correlations in iron pnictides are strong, as pointed out in Refs. [15][16][17][18] but unlike earlier studies our ab-initio method accounts for the absence of well defined Hubbard bands in the spectral functions. Our results are thus in excellent agreement with experiment and reconcile the results of apparently conflicting spectroscopies.We start with the one-particle electron Green's function in t...