Regensburg 2013 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 38: Correlated Electrons: Metal-Insulator Transition 1
TT 38.4: Vortrag
Mittwoch, 13. März 2013, 10:15–10:30, H20
Phase transitions induced by the cooperative Jahn-Teller effect: A multi-scale study of KCuF3 — •Joaquin Miranda Mena1, Erik Koch1, and Eva Pavarini2 — 1German Research School for Simulation Sciences, Forschungszentrum Jülich and RWTH Aachen University — 2Institute for Advanced Simulation and JARA, Forschungszentrum Jülich
We study the transition temperature for the structural and the orbital ordering in KCuF3. We first obtain temperature dependent dynamical matrices (TDM) of the crystalline phase by computing the energy displacements of fluorines with density functional theory (DFT) within the LSDA+U framework. Because of the Coulomb interactions, the TDM tend to be quite long ranged. To minimize the required amount of DFT calculations, we subtract the long rang Coulomb (LRC) interaction to obtain short ranged TDM that can be transformed to the disorder systems. The transition temperature is found through Monte Carlo simulations. Here the fluorine positions are sampled using the short-ranged TDM adding back the LRC by an Ewald summation; as a result disorder states can be computed fast and efficiently regardless of the size of system.