Atomistic insights into surface reactivity via density functional theory

Demirtaş, Merve
In this thesis, three different topics are investigated by using Density Functional Theory. First, an extensive study of the water gas shift reaction on Mo2C surface is carried out. CO is chosen as a probe molecule in order to understand the structural and electronic effects of the metal additives on the surface. We show that preadsorbed K atom enhences the activation and adsorption of CO molecule on the surface when compared to precious metal additives we consider, which are Pt and Au. Additionally, the presence of Pt and K stabilizes the transition state of the C-O bond scission, lowers the activation energy of this reaction. In the fourth part, the oxidation of CH3OH molecule is examined on bare and Ptdoped Au(111) surfaces. With this aim, the adsorption energies of molecules and atoms involved in the reaction of CH3OH dissociation to CH3O and H in order to obtain their stable sites. Having defined them, the activation barrier calculations are carried out on the bare Au(111) surface. Additionally, the same calculations are performed on the Pt-doped Au(111) surface in different concentrations in order to see the effect of them on the activation barrier. We show that the activation barriers are notably decreased when the number of Pt dopant atoms on the surfaces increases. In the fifth part, the interaction between the amorphous SiO2, crystal Si, oxidized crystal Si surfaces and ions of different types of etchants, which are H,F and Cu, is examined. The interaction between ions and amorphous surface is shown to be weaker than the reconstructed bare and oxydized Si surfaces. The adsorption energies are quite high for H and F ions on the reconstructed Si(001) surface. For Cu ions, the adsorption energy is improved with precovered O atom on the Si surface.


Density functional theory investigation of TiO2 anatase nanosheets
Sayın, Ceren Sibel; Toffoli, Hande; Department of Physics (2009)
In this thesis, the electronic properties of nanosheets derived from TiO2 anatase structure which acts as a photocatalyst, are investigated using the density functional theory. We examine bulk constrained properties of the nanosheets derived from the (001) surface and obtain their optimized geometries. We investigate properties of lepidocrocite-type TiO2 nanosheets and nanotubes of different sizes formed by rolling the lepidocrocite nanosheets. We show that the stability and the band gaps of the considered ...
Density functional theory calculations of small ZnmSn clusters
Katırcıoğlu, Şenay (2001-07-16)
We have investigated the structural and electronic properties of isolated neutral ZnmSn clusters for m + n less than or equal to 4 by performing density functional theory calculations at B3LYP level. We have obtained the optimum geometries, the electronic structures, and the possible dissociation channels of the clusters considered.
Electronic and structural properties of armchair SWCNT/TiO2(110)-(1 x 2) system
Tayran, C.; ÇAKMAK, MELEK; Elliatioglu, S. (Elsevier BV, 2011-03-01)
We have presented structural and electronic properties of single-walled carbon nanotubes (CNTs) with armchair chirality on the reconstructed rutile TiO2(110)-(1 x 2) surface by means of ab initio calculations using density functional theory. For the TiO2 surface reconstruction, we have adopted an added-row model which was experimentally proposed in parallel to STM patterns and theoretically agreed by first principle calculations. In this work, we have studied, as examples, two CNTs with different sizes, (3,...
Density Functional Theory Calculations on Polyacene Molecules
Pekoz, Rengin; Erkoç, Şakir (2010-03-01)
The structural and electronic properties of isolated linear and zigzag type polyacene molecules have been investigated by density functional theory calculations using B3LYP exchange-correlation functional with 6-31G(d) basis set. The zigzag polyacene molecules found to be energetically more stable than the linear structures and the optimized molecules of both types have planar geometries. In the present study, more attention has been given to the picene molecule which is a rival to pentacene molecule and ha...
Dissociation of Ph-3 and AsH3 on Ge(100)(2x1) surface
Katırcıoğlu, Şenay (World Scientific Pub Co Pte Lt, 2007-06-01)
The most stable structures for the dissociation of phosphine and arsine on Ge(100)(2x1) surface have been investigated by relative total energy calculations based on Density Functional Theory. It has been found that the thermodynamically preferred structures in the dissociation path of phosphine and arsine are the same; PH2 and AsH2 products prefer to be on a single Ge dimer bond, but PH and AsH prefer to be between the adjacent Ge dimers. According to the optimization calculations, the dissociation path st...
Citation Formats
M. Demirtaş, “Atomistic insights into surface reactivity via density functional theory,” Ph.D. - Doctoral Program, Middle East Technical University, 2018.