Gradient Corrections to Exchange Energies within Density Functional Theory
Research output: Thesis › Doctoral Thesis (compilation)
Abstract
The smallwavector expansions for the first and secondorder exchange energy kernels (secondand thirdorder functional density derivatives of the exchange energy) have been investigated. Expansion coefficients are found, both in the case of a statically screened Coulomb interaction and a 'bare' interaction. The ensuing series of gradient corrections to the local density approximation (LDA) is then given, with particular emphasis on the secondorder and fourthdegree term. Exactly calculated exchange energies for model solids are compared to a truncated series of gradient terms. It is found that the firstprinciples gradient series can improve the LDA description of the exchange energy by two orders of magnitude for metallic sp bonded systems. In the case of semiconductors the results are less accurate.
A scheme for obtaining exact DensityFunctional orbitals and eigenvalues is tested on the Neon atom. These exact properties are compared to approximate ones within two socalled Generalized Gradient Approximation schemes. The schemes are found to give an accurate total energy, whereas the exchangecorrelation potentials are of similar quality as within the LDA.
A method for obtaining total energies of solids from thirdorder perturbation theory is tried out in the case of impurities in the electron gas. The method turns out to work well for singly charged impurities.
A scheme for obtaining exact DensityFunctional orbitals and eigenvalues is tested on the Neon atom. These exact properties are compared to approximate ones within two socalled Generalized Gradient Approximation schemes. The schemes are found to give an accurate total energy, whereas the exchangecorrelation potentials are of similar quality as within the LDA.
A method for obtaining total energies of solids from thirdorder perturbation theory is tried out in the case of impurities in the electron gas. The method turns out to work well for singly charged impurities.
Details
Authors  

Research areas and keywords  Subject classification (UKÄ) – MANDATORY
Keywords

Original language  English 

Qualification  Doctor 
Awarding Institution  
Supervisors/Assistant supervisor 

Award date  1996 Jun 6 
Publisher 

Print ISBNs  9162821199 
Publication status  Published  1996 
Publication category  Research 
Externally published  Yes 
Bibliographic note
Defence details
Date: 19960606
Time: 10:15
Place: Lecture Hall B, Dept of Physics
External reviewer(s)
Name: Gritsenko, Oleg
Title: Dr
Affiliation: [unknown]

Related research output
Svendsen, PS., 1997, In : Physica Scripta. 55, 4, p. 459463
Research output: Contribution to journal › Article
Springer, M., Svendsen, PS. & Ulf von Barth, 1996, In : Physical Review B. 54, p. 17392
Research output: Contribution to journal › Article
Svendsen, P. S. & Ulf von Barth, 1996, In : Physical Review B. 54, 17402.
Research output: Contribution to journal › Article