Sökning: "GW-approximation"

Visar resultat 1 - 5 av 7 avhandlingar innehållade ordet GW-approximation.

  1. 1. Model Vertices Beyond the GW Approximation

    Detta är en avhandling från Department of Theoretical Physics, Lund University

    Författare :Mikael Hindgren; Lunds universitet.; Lund University.; [1997]
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; thermodynamics; Matematisk och allmän teoretisk fysik; statistical physics; gravitation; GW approximation; Electron self energy; Green s function; consistency; local-field corrections; vertex function; conserving approximations; variational energies; Mathematical and general theoretical physics; classical mechanics; relativity; quantum mechanics; klassisk mekanik; kvantmekanik; relativitet; statistisk fysik; termodynamik; Fysicumarkivet A:1997:Hindgren;

    Sammanfattning : We study the effects of local vertex corrections to the self energy of the electron gas. We find that a vertex derived from time-dependent density-functional theory can give accurate self energies without including the explicit time dependence of the exchange-correlation potential provided, however, that a proper decay at large momentum transfer (large q) is built into the vertex function. LÄS MER

  2. 2. Self-consistency and the GW-approximation

    Detta är en avhandling från B. Holm

    Författare :Bengt Holm; Lunds universitet.; Lund University.; [1997]
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; thermodynamics; Matematisk och allmän teoretisk fysik; Spectral Function; Greens functions; Self-energy; classical mechanics; Mathematical and general theoretical physics; Quasiparticle.; quantum mechanics; relativity; statistical physics; gravitation; klassisk mekanik; kvantmekanik; relativitet; statistisk fysik; termodynamik; Fysicumarkivet A:1997:Holm;

    Sammanfattning : The effects of self-consistency in the GW-approximation are studied. The $GWA$ is known to describe the electronic properties of a wide range of materials very well. However, the calculations made so far have not taken into account the issue of self-consistency, which is implied in the original formulation of the $GWA$. LÄS MER

  3. 3. Static and Dynamic Correlation Effects in Atoms

    Detta är en avhandling från Nils Erik Dahlen, Sölvegatan 14A, SE-223 62 Lund, Sweden

    Författare :Nils-Erik Dahlen; Lunds universitet.; Lund University.; [2002]
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; electrical; magnetic and optical properties; Condensed matter:electronic structure; relaxation; magnetic resonance; supraconductors; spectroscopy; Kondenserade materiens egenskaper:elektronstruktur; Atom- och molekylärfysik; Atomic and molecular physics; spektroskopi; magnetisk resonans; egenskaper elektriska; supraledare; magnetiska och optiska ; variational energies; double ionization; Electron correlation; laser-atom interaction; Fysicumarkivet A:2002:Dahlen; conserving approximations; Green s functions; GW-approximation;

    Sammanfattning : The thesis considers the effects of electron correlation by studying the two opposite limits of atoms in the ground state and atoms in strong laser pulses. Computational methods and theoretical approaches differ significantly due to the different physical processes that are studied in these two cases. LÄS MER

  4. 4. First principles methods for electronic structure calculations of solids

    Detta är en avhandling från Department of Theoretical Physics, Lund University

    Författare :Martin Springer; Lunds universitet.; Lund University.; [1997]
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; T-matrix; screened interaction; vertex function; GW approximation; Green function; density functional theory; gradient expansion; order N method; Physics; Fysik;

    Sammanfattning : A straightforward gradient expansion of the exchange energy of a perturbed electron gas is performed. Studied perturbations range from very weak to those that produce, e.g., a silicon-like band structure with a band gap. LÄS MER

  5. 5. Periodized Thermal Greens Functions and Applications

    Detta är en avhandling från Department of Theoretical Physics, Lund University

    Författare :Andro Sabashvili; Göteborgs universitet.; Gothenburg University.; [2013]
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; condensed matter physics; Greens function; graphene; DMFT; RPA; GW;

    Sammanfattning : This work describes a new formalism for Fermionic thermal Greens functions that are discretized in imaginary time. The discretization makes the thermal Greens function periodic in imaginary (Matsubara) frequency space and requires a generalisation of the Dyson equation and Luttinger-Ward-Baym-Kadanoff functional. LÄS MER