Search for dissertations about: "exchange functionals"

Showing result 1 - 5 of 29 swedish dissertations containing the words exchange functionals.

2. 1. van der Waals Density Functionals

   Author : Ylva Andersson; Chalmers tekniska högskola; []
   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

4. 2. Nonlocal Correlations in Density Functional Theory

   Author : Henrik Rydberg; Chalmers tekniska högskola; []
   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. 3. Theory of van der Waals bonding: from bulk materials to biomolecules

   Author : Elisa Londero; Chalmers tekniska högskola; []
   Keywords : 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;

   Abstract : 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. READ MORE

6. 4. Density Functionals for Dynamic Linear Response in Finite Systems

   Author : Maria Hellgren; Matematisk fysik; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES;

   Abstract : This dissertation investigates a new method for obtaining excited-state properties of finite, many-electron systems such as atoms, molecules and nano-systems. The method combines the merits of many-body perturbation theory and time-dependent perturbation theory and yields approximate density response functions which preserve basic physical conservation laws. READ MORE

7. 5. Theoretical Actinide Chemistry – Methods and Models

   Author : Pernilla Wåhlin; Ulf Wahlgren; Luis Seijo; Stockholms universitet; []
   Keywords : Actinide; Quantum chemistry; Wave function; Density functional theory; Solvent models; Water exchange; Molecular configurations; Multi-reference density functional method; teoretisk fysik; Theoretical Physics;

   Abstract : The chemistry of actinides in aqueous solution is important, and it is essential to build adequate conceptual models and develop methods applicable for actinide systems. The complex electronic structure makes benchmarking necessary. READ MORE