20 research outputs found

    Quasiparticle self-consistent GWGW method; a basis for the independent-particle approximation

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    We have developed a new type of self-consistent scheme within the GWGW approximation, which we call quasiparticle self-consistent GWGW (QSGWGW). We have shown that QSGWGW rather well describes energy bands for a wide-range of materials, including many where the local-density approximation fails. QSGWGW contains physical effects found in other theories such as LDA+U+U, SIC and GWGW in a satisfactory manner without many of their drawbacks (partitioning of itinerant and localized electrons, adjustable parameters, ambiguities in double-counting, etc.). We present some theoretical discussion concerning the formulation of QSGWGW, including a prescriptino for calculating the total energy. We also address several key methodological points needed for implementation. We then show convergence checks and some representative results in a variety of materials.Comment: v2:the same as previous version --but better tex file; v3:add appendix and modify introduction,mainly; v4 mainly, theoretical section (IB IC) are renewe

    All-electron self-consistent GW approximation: Application to Si, MnO, and NiO

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    We present a new kind self-consistent GW approximation (scGW) based on the all-electron, full-potential LMTO method. By iterating the eigenfunctions of the GW Hamiltonian, self-consistency in both the charge density and the quasiparticle spectrum is achieved. We explain why this form of self-consistency should be preferred to the conventional one. Then some results for Si are shown as a representative semiconductor, to establish agreement with a prior scGW calculation. Finally we consider many details in the electronic structure of the antiferromagnetic insulators MnO and NiO. Excellent agreement with experiment is shown for many properties, suggesting that a Landau quasiparticle (energy band) picture of MnO and NiO provides a reasonable description of electronic structure even in these correlated materials.Comment: 5 pages, 3 figure

    Adequacy of Approximations in GW Theory

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    We use an all-electron implementation of the GW approximation to analyze several possible sources of error in the theory and its implementation. Among these are convergence in the polarization and Green's functions, the dependence of QP levels on choice of basis sets, and differing approximations for dealing with core levels. In all GW calculations presented here, G and W are generated from the local-density approximation (LDA), which we denote as the \GLDA\WLDA approximation. To test its range of validity, the \GLDA\WLDA approximation is applied to a variety of materials systems. We show that for simple sp semiconductors, \GLDA\WLDA always underestimates bandgaps; however, better agreement with experiment is obtained when the self-energy is not renormalized, and we propose a justification for it. Some calculations for Si are compared to pseudopotential-based \GLDA\WLDA calculations, and some aspects of the suitability of pseudopotentials for GW calculations are discussed.Comment: 38 pages,6 figures. Minor Revision

    Theory of enhancement of thermoelectric properties of materials with nanoinclusions

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    Based on the concept of band bending at metal/semiconductor interfaces as an energy filter for electrons, we present a theory for the enhancement of the thermoelectric properties of semiconductor materials with metallic nanoinclusions. We show that the Seebeck coefficient can be significantly increased due to a strongly energy-dependent electronic scattering time. By including phonon scattering, we find that the enhancement of ZT due to electron scattering is important for high doping, while at low doping it is primarily due to a decrease in the phonon thermal conductivity
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