Sökning: "Exchange-correlation functionals"

Visar resultat 1 - 5 av 19 avhandlingar innehållade orden Exchange-correlation functionals.

  1. 1. van der Waals Density Functionals

    Författare :Ylva Andersson; Chalmers tekniska högskola; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; van der Waals molecules; physisorption; van der Waals interactions; density-functional theory; exchange-correlation energy; scanning-force microscopy; adhesion;

    Sammanfattning : 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. LÄS MER

  3. 2. The many-electron energy in density functional theory : from exchange-correlation functional design to applied electronic structure calculations

    Författare :Rickard Armiento; Göran Grimvall; Jens K. Nörskov; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Physics; Fysik;

    Sammanfattning : Att förutsäga egenskaper hos material och kemiska system är en viktig komponent för teoretisk och teknisk utveckling i fysik, kemi och biologi. Ett systems egenskaper styrs till stor del av dess elektrontillstånd. Datorprogram som baseras på täthetsfunktionalsteori kan beskriva elektronkonfigurationer mycket noggrant. LÄS MER

  4. 3. Theory of van der Waals bonding: from bulk materials to biomolecules

    Författare :Elisa Londero; Chalmers tekniska högskola; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; alkanes; extended systems; DNA; band structure; van der Waals Density Functional vdW-DF ; exchange functionals; Density Functional Theory; non-local correlation; layered oxides;

    Sammanfattning : Sparse matter is abundant in Nature.It encompasses systems characterized by an intrinsic low density of electrons in sizeable regions, where the van der Waals forces contribute considerably to cohesion.Given the length scale of the problem, a prediction of these materials requires appropriate tools within a quantum-mechanical framework. LÄS MER

  5. 4. Efficient Calculation of Nonlinear Spectroscopic Properties within the Time-Dependent Density Functional Theory Approximation

    Författare :Karan Ahmadzadeh; Patrick Norman; Johannes Neugebauer; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Cubic response; DFT; Response theory; Theoretical Chemistry and Biology; Teoretisk kemi och biologi;

    Sammanfattning : This thesis introduces a novel computational scheme tailored for efficient calculations of nonlinear spectroscopic observables. First, a derivation and implementation of an algorithm designed to harness the linearity of the Fock matrix construction in calculating two-photon absorption cross-sections within the self-consistent field approximation is presented. LÄS MER

  7. 5. A new generation density functional towards chemical accuracy

    Författare :Zhang Ying; Luo Yi; Head-Gordon Martin; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Bioengineering; Bioteknik;

    Sammanfattning : Density functional theory (DFT) has become the leading method in calculating theelectronic structures and properties from first principles. In practical applicationsof DFT in the frame work of Kohn-Sham (KS) method, an approximate exchange-correlation functional has to be chosen. LÄS MER