Implementation of self interaction free density functional methods and applications to dilute magnetic semiconductors
Citation:
Sri Chaitanya Das Pemmaraju, 'Implementation of self interaction free density functional methods and applications to dilute magnetic semiconductors', [thesis], Trinity College (Dublin, Ireland). School of Physics, 2008, pp 216Download Item:
Abstract:
The present thesis mainly deals with the implementation of self interaction free density
functional methods in a numerically efficient density functional theory code SIESTA and
the application of the said methods in ab-inito electronic structure calculations. We
present calculations on the polarizability of molecular chains using explicity orbital dependent
density functional methods viz., exact exchange and self interaction corrected
(SIC) functionals, which address some long standing issues in the field. We show that
SIC functionals in fact perform better than the exact exchange functional at the KLI level
of approximation. We discuss the ASIC method which is an approximate self interaction
correction scheme that is computationally in-expensive. Results for finite systems as well
as extended systems are discussed. We then discuss the electronic and magnetic structure
of defective Hafnium Oxide systems where in we show that native Hafnium vacancies exhibit
spin polarized ground states with ferromagnetic inter-defect coupling. An extensive
study on Co doped ZnO is then presented mainly focusing on the possibility for intrinsic
ferromagnetism in the material arising from native defect induced perturbations to the electronic
structure of doped Co. We show that a defect-dopant complex center formed form a
substitutional Co ion and an Oxygen vacancy can mediate long range ferromagnetic interactions.
However we attribute the experimentally observed signatures of ferromagnetism
to blocked superiparamagnetic clusters. Finally we present ab-initio electronic transport
calculations on Mn12 based single molecule magnets in a two terminal device set up. The
current-voltage (I-V) characteristics of the molecule for two different spin configurations
of the Mn12 center are studied. We show that a change in the local magnetic configuration
on the molecule can lead to a detectable change in the I-V characteristics.
Author: Pemmaraju, Sri Chaitanya Das
Advisor:
Sanvito, StefanoPublisher:
Trinity College (Dublin, Ireland). School of PhysicsNote:
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Physics, Ph.D., Ph.D. Trinity College DublinMetadata
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