Search for dissertations about: "GW approximation"

Showing result 1 - 5 of 15 swedish dissertations containing the words GW approximation.

  2. 1. Model Vertices Beyond the GW Approximation

    Author : Mikael Hindgren; Matematisk fysik; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; Matematisk och allmän teoretisk fysik; thermodynamics; 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;

    Abstract : 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. READ MORE

  4. 2. Unifying first-principles and model approaches for strongly correlated materials : Interplay between long- and short-range correlations

    Author : Fredrik Nilsson; Matematisk fysik; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; first-principle methods; strongly correlated materials; GW approximation; cRPA; random-phase approximation; dynamical mean-field theory; GW DMFT; downfolding;

    Abstract : In materials with open 3$d$ and 4$f$ shells the valence electrons are relatively localized around the atoms which leads to large electron-electron correlations. These, so called strongly correlated materials, exhibit many intriguing properties such as high $T_c$ superconductivity, colossal magneto-resistance and heavy fermion behaviour. READ MORE

  5. 3. Self-consistency and the GW-approximation

    Author : Bengt Holm; Matematisk fysik; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; Matematisk och allmän teoretisk fysik; thermodynamics; 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;

    Abstract : 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 $GWA$. READ MORE

  6. 4. Periodized Thermal Greens Functions and Applications

    Author : Andro Sabashvili; Göteborgs universitet; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; condensed matter physics; Greens function; graphene; DMFT; RPA; GW;

    Abstract : 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. READ MORE

  7. 5. Electronic Structure and Optical Properties of Solar Energy Materials

    Author : Baochang Wang; Natalia Skorodumova; Silvana Botti; KTH; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; GW; Bethe-Salpeter equation; Kinetic Monte Carlo; Density Functional Theory; Materials Science and Engineering; Teknisk materialvetenskap;

    Abstract : In this thesis, we have studied the electronic and optical properties of solar energy m-terials. The studies are performed in the framework of density functional theory (DFT), GW, Bethe-Salpeter equation (BSE) approaches and Kinetic Monte Carlo (KMC). We present four sets of results. READ MORE