Density Functionals for Dynamic Linear Response in Finite Systems
(2009) Abstract
 This dissertation investigates a new method for obtaining excitedstate properties of finite, manyelectron systems such as atoms, molecules and nanosystems. The method combines the merits of manybody perturbation theory and timedependent perturbation theory and yields approximate density response functions which preserve basic physical conservation laws. Furthermore, advanced density functionals for groundstate properties like total energies and van der Waals coefficients can be constructed from these approximations.
The thesis begins with an introduction that discusses in more detail the concepts and formulas used in the papers attached. It is followed by a summary of the main findings and an outlook. In total,... (More)  This dissertation investigates a new method for obtaining excitedstate properties of finite, manyelectron systems such as atoms, molecules and nanosystems. The method combines the merits of manybody perturbation theory and timedependent perturbation theory and yields approximate density response functions which preserve basic physical conservation laws. Furthermore, advanced density functionals for groundstate properties like total energies and van der Waals coefficients can be constructed from these approximations.
The thesis begins with an introduction that discusses in more detail the concepts and formulas used in the papers attached. It is followed by a summary of the main findings and an outlook. In total, four original papers are included.
Paper I is concerned with the random phase approximation for the total energy and the corresponding KohnSham (KS) potential. While total energies are far too negative the potentials produce very accurate ionization potentials.
Paper II investigates the response function of the timedependent exactexchange (TDEXX) approximation for obtaining static polarizabilities, van der Waals coefficients and some low excitation energies. The results are very close to results obtained from timedependent HartreeFock theory showing that the method accurately reproduce results from the more demanding BetheSalpeter approach.
In Paper III some important findings regarding the exactexchange kernel are presented. The optical absorption spectra is calculated and the results show that at higher energies the approximation is illbehaved leading to a response function with the wrong analytic structure. A new derivation of Fanoparameters based on adiabatic TDDFT is also given.
In Paper IV the adiabatic approximation to TDEXX is used to obtain an advanced functional for the total energy, yielding both excellent total energies and KS potentials. van der Waals coefficients are shown to be very sensitive to the groundstate density and when calculated in TDEXX using a correlated density, results are remarkably improved. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/record/1468210
 author
 Hellgren, Maria ^{LU}
 supervisor
 opponent

 Rubio, Angel, Departemento de Fisica de Materiales, Facultad de Quimicas, Universidad del Pais Vasco, Espana
 organization
 publishing date
 2009
 type
 Thesis
 publication status
 published
 subject
 pages
 100 pages
 defense location
 Lundmarksalen, Astronomihuset
 defense date
 20090921 10:15
 language
 English
 LU publication?
 yes
 id
 67758d056e5c4c2a8474b41426a673cf (old id 1468210)
 date added to LUP
 20090831 09:37:20
 date last changed
 20160919 08:45:16
@misc{67758d056e5c4c2a8474b41426a673cf, abstract = {This dissertation investigates a new method for obtaining excitedstate properties of finite, manyelectron systems such as atoms, molecules and nanosystems. The method combines the merits of manybody perturbation theory and timedependent perturbation theory and yields approximate density response functions which preserve basic physical conservation laws. Furthermore, advanced density functionals for groundstate properties like total energies and van der Waals coefficients can be constructed from these approximations.<br/><br> <br/><br> The thesis begins with an introduction that discusses in more detail the concepts and formulas used in the papers attached. It is followed by a summary of the main findings and an outlook. In total, four original papers are included.<br/><br> Paper I is concerned with the random phase approximation for the total energy and the corresponding KohnSham (KS) potential. While total energies are far too negative the potentials produce very accurate ionization potentials.<br/><br> Paper II investigates the response function of the timedependent exactexchange (TDEXX) approximation for obtaining static polarizabilities, van der Waals coefficients and some low excitation energies. The results are very close to results obtained from timedependent HartreeFock theory showing that the method accurately reproduce results from the more demanding BetheSalpeter approach.<br/><br> In Paper III some important findings regarding the exactexchange kernel are presented. The optical absorption spectra is calculated and the results show that at higher energies the approximation is illbehaved leading to a response function with the wrong analytic structure. A new derivation of Fanoparameters based on adiabatic TDDFT is also given.<br/><br> In Paper IV the adiabatic approximation to TDEXX is used to obtain an advanced functional for the total energy, yielding both excellent total energies and KS potentials. van der Waals coefficients are shown to be very sensitive to the groundstate density and when calculated in TDEXX using a correlated density, results are remarkably improved.}, author = {Hellgren, Maria}, language = {eng}, pages = {100}, title = {Density Functionals for Dynamic Linear Response in Finite Systems}, year = {2009}, }