Andrey Kutepov

Electronic correlation and transport properties of nuclear fuel materials

The electronic structures and transport properties of a series of actinide monocarbides, mononitrides, 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.

Magnetic anisotropic effects and electronic correlations in MnBi ferromagnet

The electronic structure and numerous magnetic properties of MnBi magnetic systems are investigated using local spin density approximation (LSDA) with on-cite Coulomb correlations (LSDA+U) included. We show that the inclusion of Coulomb correlations provides a much better description of equilibrium magnetic moments on Mn atoms as well as the magnetic anisotropy energy behavior with temperature and magneto-optical effects. We found that the inversion of the anisotropic pairwise exchange interaction between Bi atoms is responsible for the observed spin reorientation transition at 90 K. This interaction appears as a result of strong spin orbit coupling on Bi atoms, large magnetic moments on Mn atoms, significant p-d hybridization between Mn and Bi atoms, and it depends strongly on lattice constants (anisotropic Bi-Bi exchange striction). A better agreement with the magneto-optical Kerr measurements at higher energies is obtained. We also present the detailed investigation of the Fermi surface, the de Haas–van Alphen effect, and the x-ray magnetic circular dichroism in MnBi.

Electronic structure of Pu and Am metals by self-consistent relativistic GWmethod

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 Matsubaras 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.

Ground-state properties of simple elements from GW calculations

A self-consistent implementation of Hedins GW perturbation theory is introduced. This finite-temperature method uses Hartree-Fock wave functions obtained with full potential linear augmented plane-wave method to represent Greens function. With our approach we are able to calculate total energy as a function of the lattice parameter. Ground-state properties calculated for Na, Al, and Si compare well with experimental data.

Self-consistent solution of Hedin's equations: Semiconductors and insulators

The band gaps of a few selected semiconductors/insulators are obtained from the self-consistent solution of the Hedins equations. Two different schemes to include the vertex corrections are studied: (i) the vertex function of the first-order (in the screened interaction

Electronic structure of Na, K, Si, and LiF from self-consistent solution of Hedin's equations including vertex corrections

W

Strength and scales of itinerant spin fluctuations in 3d paramagnetic metals

) is applied in both the polarizability

Linearized self-consistent quasiparticle GW method: Application to semiconductors and simple metals

P

Self-consistent GW determination of the interaction strength: Application to the iron arsenide superconductors

and the self-energy

Atomistic simulations of helium dynamics in a plutonium lattice

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