Regensburg 2013 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 40: Poster Session Correlated Electrons

TT 40.33: Poster

Wednesday, March 13, 2013, 15:00–19:00, Poster D

Ab-initio Hubbard parameters for molecular crystals by a symmetry decomposed Ewald method — •Michael M. E. Baumgärtel and Erik Koch — German Research School for Simulation Sciences, Forschungszentrum Jülich, and RWTH Aachen University, 52425 Jülich, Germany

For strongly correlated molecular crystals we determine realistic Hubbard parameters ab-initio. Restricting to electrons in the partially filled bands, screening by the other electrons renormalizes the Hubbard parameters. The intra-molecular screening is treated within DFT, while inter-molecular Coulomb interaction is modeled by a lattice of distributed polarizabilities. Charging of a molecular orbital breaks the periodic symmetry of dipole interactions. By separating the linear response, we obtain a periodic dipole-dipole interaction operator that is independent of the actual polarization pattern. Inverting this operator gives the self-consistent linear screening. In reciprocal space the interaction matrix is low-dimensional, but long-range. However, we obtain rapidly converging matrix elements through an optimized Ewald-summation.

We present eigen-spectra of Fourier transformed dipole interaction matrices. Employed on a Brillouin zone grid our fast diagonalization method yields the Hubbard parameters, both on-site and long-ranged, for any charging of molecular orbitals. We demonstrate our method for Fullerenes as well as TTF-TCNQ crystals.