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SUMMARY:Quasiparticle Self-consistent GW Approximation as a Universal Fram
 ework for Electronic Structure - Prof Mark v. Schilfgaarde\, King's Colleg
 e London
DTSTART:20120426T131500Z
DTEND:20120426T141500Z
UID:TALK37678@talks.cam.ac.uk
CONTACT:Dr G Moller
DESCRIPTION:A new type of self-consistent scheme within the GW approximati
 on is presented\, which we call the quasiparticle self-consistent GW (QSGW
 ) approximation. It is based on a kind of self-consistent perturbation the
 ory\, where the self-consistency is used to minimize the difference betwee
 n the many-body and single-particle Hamiltonians. QSGW describes optical p
 roperties in a wide range of materials rather well\, including cases where
  the local-density and LDA-based GW approximations fail qualitatively. Sel
 f-consistency dramatically improves agreement with experiment\, and is som
 etimes essential. QSGW avoids some formal and practical problems encounter
 ed in conventional self-consistent GW\, which will be discussed. It handle
 s both itinerant and correlated electrons on an equal footing\, without an
 y ambiguity about how a localized state is defined\, or how double-countin
 g terms should be subtracted. Weakly correlated materials such as Na and s
 p semiconductors are described with uniformly high accuracy. Discrepancies
  with experiment are small and systematic\, and can be explained in terms 
 of the approximations made.\n\nIts consistently high accuracy make QSGW a 
 versatile method that can reliably predict critical energy band properties
  of graphene\, CuInSe2\, CaFe2As2 and NiO in a unified framework. Many oth
 er properties attendant to the electronic structure can be calculated\, su
 ch as magnetic excitations\, the Auger recombination process\, the transmi
 ssion through a metal-semiconductor contact. In principle it can serve bot
 h as a framework to construct effective Hamiltonians for many-body physics
 \, and as an engine to build models for device design from first principle
 s\, with unprecedented reliability. How to do this in practice is a major 
 challenge today. I will briefly present some discussion of each.
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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