Sökning: "Kohn-Sham density functional theory"

Visar resultat 1 - 5 av 16 avhandlingar innehållade orden Kohn-Sham density functional theory.

1. 1. Foundation of Density Functionals in the Presence of Magnetic Field

   Författare :Andre Laestadius; Michael Benedicks; Trygve Helgaker; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Current density functional theory; Hohenberg-Kohn theorems; paramagnetic current density functionals; Kohn-Sham theory; Levy-Lieb functional; variational principle; N-representable; degeneracy; Mathematics; Matematik;

   Sammanfattning : This thesis contains four articles related to mathematical aspects of Density Functional Theory.In Paper A, the theoretical justification of density methods formulated with current densities is addressed. It is shown that the set of ground-states is determined by the ensemble-representable particle and paramagnetic current density. LÄS MER

3. 2. Theoretical prediction of properties of atomistic systems : Density functional theory and machine learning

   Författare :Alexander Lindmaa; Rickard Armiento; Igor Abrikosov; Torbjörn Björkman; Linköpings universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY;

   Sammanfattning : The prediction of ground state properties of atomistic systems is of vital importance in technological advances as well as in the physical sciences. Fundamentally, these predictions are based on a quantum-mechanical description of many-electron systems. LÄS MER

4. 3. Molecular Quadratic Response Properties with Inclusion of Relativity

   Författare :Johan Henriksson; Patrick Norman; Juha Vaara; Linköpings universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; relativistic quantum chemistry; molecular physics; clamping levels; four-component Hartree-Fock theory; Kohn-Sham density functional theory; response theory; nonlinear optics; second-harmonic generation; two-photon absorption; excited state properties; optical power limiting; Computational physics; Beräkningsfysik;

   Sammanfattning : This thesis concerns quadratic response properties and their application to properties in Jablonski diagrams such as resonant two-photon absorption and excited state absorption. Our main interest lies in optical power limiting applications, and in this context, molecules containing heavy metal atoms prove superior. LÄS MER

5. 4. Matrix Algebra for Quantum Chemistry

   Författare :Emanuel H. Rubensson; Pawel Salek; Stefan Goedecker; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; linear scaling; reduced complexity; electronic structure; density functional theory; Hartree-Fock; density matrix purification; congruence transformation; inverse factorization; eigenvalues; eigenvectors; numerical linear algebra; occupied subspace; canonical angles; invariant subspace; Theoretical chemistry; Teoretisk kemi;

   Sammanfattning : This thesis concerns methods of reduced complexity for electronic structure calculations.  When quantum chemistry methods are applied to large systems, it is important to optimally use computer resources and only store data and perform operations that contribute to the overall accuracy. LÄS MER

7. 5. Magnetic Resonance Parameters of Radicals Studied by Density Functional Theory Methods

   Författare :Lyudmyla Telyatnyk; KTH; []
   Nyckelord :electronic g-tensor; hyperfine coupling constant; nuclear shielding tensor; spin restricted DFT; restricted-unrestricted appoach;

   Sammanfattning : The recent state of art in the magnetic resonance area putsforward the electron paramagnetic resonance, EPR, and nuclearmagnetic resonance, NMR, experiments on prominent positions forinvestigations of molecular and electronic structure. A mostdifficult aspect of such experiments is usually the properinterpretation of data obtained from high-resolution spectra,that, however, at the same time opens a great challenge forpure theoretical methods to interpret the spectral features. LÄS MER