Sökning: "density functional theory"

Visar resultat 1 - 5 av 525 avhandlingar innehållade orden density functional theory.

  1. 1. Nonlocal Correlations in Density Functional Theory

    Författare :Henrik Rydberg; [2001]
    Nyckelord :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;

    Sammanfattning : 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. LÄS MER

  2. 2. Challenges in Enzyme Catalysis - Photosystem II and Orotidine Decarboxylase A Density Functional Theory Treatment

    Detta är en avhandling från Stockholm : Fysikum

    Författare :Marcus Lundberg; Margareta Blomberg; Per Siegbahn; Jeremy Harvey; [2005]
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; photosystem II; oxyl radical; manganese systems; orotidine decarboxylase; reaction mechanism; density functional theory; NATURAL SCIENCES Chemistry Theoretical chemistry Quantum chemistry; NATURVETENSKAP Kemi Teoretisk kemi Kvantkemi;

    Sammanfattning : Possibly the most fascinating biochemical mechanism remaining to be solved is the formation of oxygen from water in photosystem II. This is a critical part of the photosynthetic reaction that makes solar energy accessible to living organisms. LÄS MER

  3. 3. Manganese and Iron Heterodimers and Homodimers in Enzymes : Insights from Density Functional Theory

    Detta är en avhandling från Stockholm : Department of Physics, Stockholm University

    Författare :Katarina Roos; Per Siegbahn; Margareta R. A. Blomberg; Frank Neese; [2012]
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Ribonucleotide reductase; manganese; iron; density functional theory; kemisk fysik; Chemical Physics;

    Sammanfattning : The enzyme ribonucleotide reductase (RNR) catalyzes the reduction of ribonucleotides to deoxyribonucleotides, the building blocks of DNA, and is essential for all organisms. Canonical class I RNR R2 proteins use a diiron cofactor to generate a tyrosyl radical, which is required for catalysis. LÄS MER

  4. 4. Atomistic modelling of functional solid oxides for industrial applications Density Functional Theory, hybrid functional and GW-based studies

    Detta är en avhandling från Stockholm : KTH

    Författare :Cecilia Århammar; Rajeev Ahuja; Steven Louie; [2011]
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; density functional theory; oxides; GW; NATURAL SCIENCES Physics Condensed matter physics; NATURVETENSKAP Fysik Kondenserade materiens fysik; NATURAL SCIENCES Physics Condensed matter physics Magnetism; NATURVETENSKAP Fysik Kondenserade materiens fysik Magnetism; NATURAL SCIENCES Physics Condensed matter physics Defects and diffusion; NATURVETENSKAP Fysik Kondenserade materiens fysik Defekter och diffusion;

    Sammanfattning : In this Thesis a set of functional solid oxides for industrial applications have been addressed by first principles and thermodynamical modelling. More specificially, measurable quantities such as Gibbs free energy, geometry and electronic structure have been calculated and compared when possible with experimental data. LÄS MER

  5. 5. Applied density functional theory : calculating structures and energies on ribonucleotide reductase and polycyclic aromatic hydrocarbons

    Detta är en avhandling från Stockholm : Stockholm University

    Författare :Kyung-Bin Cho; [2003]
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES;

    Sammanfattning : .... LÄS MER