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TT: Fachverband Tiefe Temperaturen

TT 6: Postersession Correlated Electrons: (General) Theory, Low-Dimensional Systems, Kondo Physics, Heavy Fermions, Quantum-Critical Phenomena

TT 6.24: Poster

Montag, 23. März 2009, 13:00–16:45, P1A

From solid to cluster – a computational study on the model compound Li₂CuO₂ — •Ulrike Nitzsche¹, Stefan-Ludwig Drechsler¹, and Helge Rosner² — ¹IFW Dresden, PF 270116, 01171 Dresden — ²MPI CPfS Dresden, Nöthnitzer Str. 40, 01187 Dresden

The treatment of strong electron correlations is one of the major challenges in modern solid state physics and chemistry. Two standard approaches tackle the problem from opposite directions: In principle, quantum chemistry can deal with strong correlations exactly, but only for small clusters. Thus, finite size effects and the embedding of the clusters have to be controlled. On the other hand, periodic 3D compounds can be calculated reliably in DFT codes, but the correlations are treated in a very approximate manner, often including external parameters like in the widely used LSDA+U method. Using the 1D model compound Li₂CuO₂ as an example, we present a computational study on the DFT level, aiming to a controlled, smooth transition from a 3D system to a cluster while preserving the most relevant physics of the system. Step by step, the structural complexity of the system is reduced, controlling the leading interactions by a tight binding procedure. Our study shall provide deeper insight into the implications caused by the different levels of approximations.