Regensburg 2019 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 17: Poster Session: Correlated Electrons 1

TT 17.44: Poster

Monday, April 1, 2019, 15:00–18:30, Poster D

Building effective models for correlated electron systems — •Qian Zhang and Erik Koch — Institute for Advanced Simulation, Forschungszentrum Jülich, 52428 Jülich, Germany

To understand strongly correlated systems, we must confront the many-body problem. Our starting point is density functional calculations for individual atoms and ions to obtain realistic basis functions and the corresponding matrix elements. In particular, we focus on the open-shell orbitals, which have the strongest correlation effects. For individual atoms and ions, we collected the Slater-Condon and spin-orbit parameters from the resulting self-consistent radial wave functions and potentials. We analyzed the trends of the parameters systematically across the periodic table, which allowed us to calculate atomic open-shell spectra in LS-, intermediate-, and jj-coupling schemes.

While atomic orbitals are mutually orthogonal within a single atom, they are, in general, non-orthogonal for atoms on different lattice sites. We studied and developed efficient multi-center integral techniques for evaluating orbital overlaps, which are essential for performing orbital orthogonalization. This allowed us to study atomic orbitals in various crystal structures. To orthogonalize the basis orbitals, we applied the Löwdin symmetric orthogonalization scheme, which minimizes the orbital modification. For the resulting orbitals, we studied the deformation due to orthogonalization and investigated the modification of the matrix elements compared with the atomic ones.