dc.contributor.author | Davari, Nazanin | |
dc.date.accessioned | 2015-10-28T13:24:08Z | |
dc.date.available | 2015-10-28T13:24:08Z | |
dc.date.issued | 2015 | |
dc.identifier.isbn | 978-82-326-0939-0 | |
dc.identifier.issn | 1503-8181 | |
dc.identifier.uri | http://hdl.handle.net/11250/2358350 | |
dc.description.abstract | Insulating liquids are often used as a dielectric barrier between two electrodes
in high-voltage devices and may suffer a breakdown in high electric
fields. Breakdown happens when a conductive plasma channel, a
streamer, is created in high field regions which propagates through the
barrier and bridges the gap between two electrodes. This phenomenon is
influenced by the field-dependent molecular properties of the insulating
liquid. Among the different properties, the molecular ionization potential
(IP) and excitation energies are investigated for molecules relevant
for insulating liquids. It is demonstrated how density functional theory
(DFT) can be used to propose suitable molecules for the design of new
insulating liquids. A model based on constrained DFT is developed for
the calculation of field-dependent IP and time-dependent DFT is used to
study a few lowest excitation energies in the field. For a dielectric liquid
in the electric field, energy is added continuously to the liquid. The liquid
releases energy by emitting heat or light in the UV/VIS region. Thus,
the excitation energies of molecules in liquids may be important in the
streamer experiments. The IP decreases strongly with increasing the field,
while the excitation energies are weakly dependent on the field. There is
a threshold field for different types of molecules that above it a two-state
system consisting of the electronic ground state and the ionized state is
obtained.
The local electric field is an important parameter in modeling the
streamer behavior and is different from the external electric field. A forcefield
model is developed to calculate the response of the local field to
the external field (local field factor). The local field factors are calculated
for liquid benzene by combining the force-field model with the molecular
dynamics simulations. The local field factor increases significantly at the
absorption frequency for liquid benzene. The force-field model can also
be used to calculate different dielectric properties of liquids. | nb_NO |
dc.language.iso | eng | nb_NO |
dc.publisher | NTNU | nb_NO |
dc.relation.ispartofseries | Doctoral thesis at NTNU;2015:141 | |
dc.relation.haspart | Paper 1: Davari, Nazanin; Åstrand, Per-Olof; Ingebrigtsen, Stian; Unge, Mikael. Excitation energies and ionization potentials at high electric fields for molecules relevant for electrically insulating liquids. Journal of Applied Physics 2013 ;Volum 113. s
<a href="http://dx.doi.org/10.1063/1.4800118" target="_blank"> http://dx.doi.org/10.1063/1.4800118</a>
(C) 2013 American Institute of Physics | nb_NO |
dc.relation.haspart | Paper 2: Davari, Nazanin; Åstrand, Per-Olof; Van Voorhis, Troy. Field-dependent ionisation potential by constrained density functional theory. Molecular Physics 2013 ;Volum 111.(9-11) s. 1456-1461.
Is not included due to copyright available at
<a href="http://dx.doi.org/10.1080/00268976.2013.800243" target="_blank"> http://dx.doi.org/10.1080/00268976.2013.800243</a> | nb_NO |
dc.relation.haspart | Paper 3: Davari, Nazanin; Åstrand, Per-Olof; Unge, Mikael; Lundgaard, Lars Esben; Linhjell, Dag. Field-dependent molecular ionization and excitation energies: Implications for electrically insulating liquids. AIP Advances 2014 ;Volum 4.(3)
<a href="http://dx.doi.org/10.1063/1.4869311" target="_blank"> http://dx.doi.org/10.1063/1.4869311</a>
All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported license | nb_NO |
dc.relation.haspart | Paper 4: Davari, Nazanin; Åstrand, Per-Olof; Unge, Mikael. Density-functional calculations of field-dependent ionization potentials and excitation energies of aromatic molecules. Chemical Physics 2015 ;Volum 447. s. 22-29
<a href="http://dx.doi.org/10.1016/j.chemphys.2014.11.023" target="_blank"> http://dx.doi.org/10.1016/j.chemphys.2014.11.023</a>
This article is reprinted with kind permission from Elsevier, sciencedirect.com | nb_NO |
dc.relation.haspart | Paper 5: Davari, Nazanin; Haghdani, Shokouh; Åstrand, Per-Olof; Schatz, George C.. Local electric field factors by a combined charge-transfer and point-dipole interaction model. RSC Advances 2015 ;Volum 5.(40) s. 31594-31605
<a href="http://dx.doi.org/10.1039/c5ra04183j" target="_blank"> http://dx.doi.org/10.1039/c5ra04183j</a>
This journal is © The Royal Society of Chemistry 2015 | nb_NO |
dc.relation.haspart | Paper 6: N. Davari, C. D. Daub, P.-O. Åstrand, and M. Unge, “Local electric field factors and dielectric properties of liquid benzene. this manuscript has been accepted and published in Journal of Physical Chemistry B
<a href="http://dx.doi.org/10.1021/acs.jpcb.5b07043" target="_blank"> http://dx.doi.org/10.1021/acs.jpcb.5b07043</a>
Reproduced with permission from Journal of Physical Chemistry B
(C) 2015 American Chemical Society. | nb_NO |
dc.title | Molecular modeling of ionization processes relevant for electrically insulating liquids | nb_NO |
dc.type | Doctoral thesis | nb_NO |
dc.subject.nsi | VDP::Mathematics and natural science: 400::Chemistry: 440 | nb_NO |