Search for dissertations about: "local density approximation"

Showing result 1 - 5 of 62 swedish dissertations containing the words local density approximation.

  1. 1. Model Vertices Beyond the GW Approximation

    University dissertation from Department of Theoretical Physics, Lund University

    Author : Mikael Hindgren; [1997]
    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

  2. 2. van der Waals Density Functionals

    University dissertation from Department of Theoretical Physics, Lund University

    Author : Ylva Andersson; [1996]
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; van der Waals molecules; physisorption; van der Waals interactions; density-functional theory; exchange-correlation energy; scanning-force microscopy; adhesion;

    Abstract : Methods using local or semi local approximations (LDA, GGA etc.) for the exchange-correlation energy in the density-functional theory (DFT) do not include van der Waals interactions. READ MORE

  3. 3. Structure and energetics of kappa alumina (-Al2O3) calculated from first principles

    University dissertation from Department of Theoretical Physics, Lund University

    Author : Yashar Yourdshahyan; [1996]
    Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; electronic properties; structure; plane-waves; local-density-approximation; stability; ceramics materials; Al2O3 K-phase; pseudopotentials; density-functional theory;

    Abstract : .... READ MORE

  4. 4. Nonlocal Correlations in Density Functional Theory

    University dissertation from Department of Theoretical Physics, Lund University

    Author : Henrik Rydberg; [2001]
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; bonding; GGA; adhesion; graphene; DFT; exchange; adsorption; LDA; first principles; polarization; vdW; determinants; correlation; graphite; surface states; van der Waals; density-functional theory; physisorption; nonlocal; functional;

    Abstract : In Density Functional Theory, the widely used local and semilocal approximations to the exchange-correlation energy, the local density approximation (LDA) and the generalized gradient approximations (GGAs), lack a physical description of truly nonlocal correlation effects, which are absolutely essential for a proper description of soft matter. A scheme is proposed that provides a basis for systematic improvements beyond LDA and GGA, including correlations at intermediate and long range, giving rise to bonds of pure van der Waals type as well as more intricate, intermediate-range correlation bonds. READ MORE

  5. 5. Van der Waals Interactions in Density Functional Theory

    University dissertation from Department of Theoretical Physics, Lund University

    Author : Erika Hult; [1999]
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; van der Waals interaction; exchange-correlation energy; adhesion; intermolecular forces; physisorption; density functional theory;

    Abstract : Density functional theory is a very important method for calculating ground-state properties for atoms, molecules and solids. Albeit exact in principle, its implementation requires an approximation for the so-called exchange-correlation energy. READ MORE