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Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 25: Focussed session: Frontiers of electronic structure theory: Strong correlations from first principles II (jointly with TT)

O 25.4: Talk

Tuesday, March 27, 2012, 11:30–11:45, HE 101

Local Density Approximation for Gutzwiller wavefunctions. A SIESTA implementation and a case study: double-exchange magnetism in bulk iron. — •Giovanni Borghi1, Michele Fabrizio2,3, and Erio Tosatti2,31Theory and Simulation of Materials, EPFL, Lausanne, Switzerland — 2SISSA, Trieste, Italy — 3ICTP, Trieste, Italy

By means of the constrained-search formulation of Density Functional Theory [1], the Kohn-Sham auxiliary system of non-interacting electrons can be generalized to a system of particles that are coupled through local Hubbard-type interactions, and whose ground-state wavefunction is computed within Gutzwiller Variational Method. The resulting Gutzwiller Density Functional is a natural extension of DFT+U functionals, with an additional set of many body parameters that have to be optimized together with the density. Among these, a band-mass renormalization parameter à la Landau accounts for the reduced mobility of correlated particles and their suppressed kinetic energy. We show how the increased flexibility of the Gutzwiller Density Functional can be exploited to better understand the origin of magnetism in transition metals. A comparison of total energies of the paramagnetic and ferromagnetic phases of iron suggests the double-exchange rather than the Stoner mechanism as an explanation of magnetic ordering in this system [2].
[1] M. Levy, Proc. Natl. Acad. Sci. USA 76, 6062 (1979); E. Lieb, Int. J. Quantum Chem. 24, 243 (1983).
[2] GB, M. Fabrizio and E. Tosatti, in preparation.

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