Local reactivity of bimetallic overlayer and cluster systems [Elektronische Ressource] / Ataollah Roudgar

Markus Lischka

Informations

• Publié par: technische_universitat_munchen
• Publié le: 01 janvier 2004
• Nombre de lectures: 15
• Langue: English
• Poids de l'ouvrage: 19 Mo

Extrait

Local reactivity of bimetallic overlayer and
cluster systems
Ataollah RoudgarTechnische Universitat Munc hen
Physik-Department T30
Univ.-Prof. Dr. A. Gro
Local reactivity of bimetallic overlayer
and cluster systems
Ataollah Roudgar
Vollstandiger Abdruck der von der Fakultat fur Physik der Technischen Universitat
Munchen zur Erlangung des akademischen Grades eines
Doktors der Naturwissenschaften (Dr. rer. nat.)
genehmigten Dissertation.
Vorsitzender: Univ.-Prof. Dr. U. Stimming
Prufer der Dissertation: 1.rof. Dr. A. Gro
2. Univ.-Prof. Dr. M. Kleber
Die Dissertation wurde am 29. Marz 2004 bei der Technischen Universitat Munc hen
eingereicht und durch die Fakultat fur Physik am 8. April 2004 angenommen. Abstract
The adsorption of atomic hydrogen and molecular CO on Pd and Cu overlayers on Au
in the presence and absence of water and also Pd clusters supported on the substrates
is studied using density functional theory. First it is demonstrated that both surface
strain and substrate interaction e ects contribute to the modi cation of the reactivity
of the overlayer system. We found a maximum of the binding energies of both H and
CO on two Pd overlayers on Au(111) and Au(100). The second part of this thesis
is concerned with the adsorption on small Pd clusters supported by Au(111). The
adsorption energies on Pd clusters turn out to be less than on corresponding Pd/Au
overlayerwhichis aconsequenceofthereducedatomic distancesintheclusterandthe
cluster-support interaction. The H and CO adsorption energies on the Pd/Au(111)
overlayer in the presence of water are modi ed by less than 10% by the most stable
H O bilayer compared to the clean surface. This indicates that theoretical adsorption2
studiesatthesolid-vacuuminterfacemightalsoberelevantforthesolid-liquidinterface.
iiiZusammenfassung
MittelsDichtefunktionaltheoriewirddieAdsorptionvonatomaremHundmolekularem
CO an dunnen Pd- und Cu-Schichten und Pd-Clustern auf einem Goldsubstrat unter-
sucht. Ebenso wird der Ein uss von Wasser auf die Adsorptionsenergien betrachtet.
Sowohl die ber achenverspannung als auch die Substratwechselwirkungse ekte tregen
zur Anderung der Reaktivitat des Schichtsystems bei. Die Bindungsenergien von H
und CO ist maximal fur zwei Pd-Schichten auf Au(111) und Au(100). Bei der Ad-
sorption an kleinen Pd-Clustern auf Au(111) stellt sich heraus, da die Adsorptions-
energien geringer sind als auf der entsprechenden Pd/Au-Schicht als Folge verringerter
Atomabstnde im Cluster und der Wechselwirkung mit dem Substrat. Die H- und CO-
Adsorptionsenergien auf der Pd/Au(111)-Schicht ndern sich um weniger als 10% in
Anwesenheit von Wasser. Das weist darauf hin, da theoretische Studien zur Adsorp-
tion an der Festkor per-Vakuum Grenz ache auch fur die fest- ussig Grenz ache von
Bedeutung sein konnen
vAcknowledgments
First and most importantly, it is a pleasure to thank my supervisor, Prof. Dr. Axel
Gro , for oering me the opportunity to work on this interesting and exciting topic
and do a doctoral thesis in his group. I am grateful for his support and the chance to
present and discuss my results with him and at the number of conferences.
I would also like to thank my colleagues of the T30g group, Markus Lischka and
Christian Mosch for answering me a lot of questions regarding the code and running
simulations on various platforms. I would also like to thank Christian Bach, Prof. Dr.
WilhelmBrenig, ArezooDianat, SungSakongforalltheinterestingdiscussionswehad
together. I owe a considerable debt to my ex-colleges from Max-Planck-Institute in
Stuttgart, Ari Seitsonen and Daniel Aktah for the helpful discussions. Without Ari I
would hardly have managed to get to know such a nice group in Munich. Moreover,
I wish to thank Georg Kresse, the main author of VASP, for the assistance with his
enormous piece of software.
Part of the computational work was done on the high performance computing fa-
cilities of the Leibniz-Rechenzentrum within the t2101 project, and I am indebted to
their administrative team for providing such an excellent computational working envi-
ronment and support. Furthermore, I also would like to acknowledge nancial support
by Deutsche Forschungsgemeinschaft.
There are always people behind the scenes, whose support is nonetheless indis-
pensable. Most of all, I am grateful for the continual encouragement of my parents,
my brother and my sisters. Without naming them individually, I nally thank many
friends of mine for their share in recreational activities, which rank highly among the
preconditions for creative work of any kind.
Munc hen Ataollah Roudgar
April 2004
vii