Hatice Kökten

STRUCTURAL AND ELECTRONIC PROPERTIES OF c-BN(110) SURFACE AND SURFACE POINT DEFECTS

The surface structure, surface energy, and surface vacancy formation energy for B and N vacancy of the cubic boron nitride (c-BN)(110) surface have been investigated by performing Hartree-Fock and DFT calculations. Results are compared with available literature values. The vacancy formation energies [unrelaxed

PHASE CHANGES IN ICOSAHEDRAL 54-, 55-, 56-ATOM PLATINUM CLUSTERS

(E_f^\circ)

ON THE STRUCTURAL AND ENERGETIC FEATURES OF SMALL METAL CLUSTERS: Nin, Cun, Pdn, Ptn, AND Pbn; n=3–13

and relaxed (Ef)] are reported for the first time for c-BN(110).

ENERGETICS OF ARSENIC TERMINATED GaAs(001) SURFACES

Using the Voter and Chen version of an embedded-atom model, derived by fitting simultaneously to experimental data both the diatomic molecule and bulk platinum, we have studied the melting behavior of free, icosahedral, 54-, 55- and 56-atom platinum clusters in the molecular dynamics simulation technique. We present an atom-resolved analysis method that includes physical quantities such as the root-mean-square bond-length fluctuation and coordination number for individual atoms as functions of temperature. The effect of a central atom in the icosahedral structure to the melting process is discussed. The results show that the global minimum structures of the 54-, 55- and 56-atom Pt clusters do not melt at a specific temperature, rather, melting processes take place over a finite temperature range. The heat capacity peaks are not δ-functions, but instead remain finite. An ensemble of clusters in the melting region is a mixture of solid-like and liquid-like clusters.

Oxygen-doped c-BN(110) surface: DFT calculations

Using an empirical potential energy function parametrized for each of the Ni, Cu, Pd, Pt, and Pb systems, minimum-energy structures of Nin, Cun, Pdn, Ptn, and Pbn (n=3–13) microclusters have been determined by performing molecular-dynamics simulations. The structural and energetic features of the obtained microclusters have been investigated.

OPTICAL TRANSITIONS IN A PARABOLIC GaAs/Ga1-xAlxAs SUPERLATTICES

We have investigated systematically the energetics of arsenic terminated GaAs(001) surfaces. Available surface models proposed in the literature have been considered, and relaxation and surface energies of each model have been calculated using an empirical many-body potential energy function comprising two and three-body atomic interactions.

Chemisorption of a p-adsorbate on perovskites

Density functional theory calculations have been performed to investigate the structural and electronic properties for both unrelaxed and relaxed cases of oxygen-doped c-BN(110) surface. Oxygen atom has been substituted in a neutral charge state on both the B site (OB) and the N site (ON). Defect formation energies, [unrelaxed (E°f) and relaxed (Ef)], and relaxation energies, Er, have been calculated. It has been found that substitution ON is more probable, moreover the ON causes an inward relaxation of the first neighbor surface B atom.

Structural and electronic properties of single-wall ZnO nanotubes

We have performed self-consistent field (SCF) calculations of the electronic structure of GaAs/Ga1-xAlxAs superlattices with parabolic potential profile within the effective mass theory. We have calculated the optical transition matrix elements involving transitions from the hole states to the electron states, and we have also computed the oscillator strength matrix elements for the transitions among the electron states.

Energetics and structural properties of carbon and oxygen doped hexagonal boron nitride sheets

Abstract The chemisorption of an oxygen adatom on the (0 0 1) surface of a perovskite crystal is examined parametrically. An empirical tight-binding method is used in the calculations. The adatom is assumed to chemisorb in a head-on position to the surface cation and the effects of the following parameters are investigated: the orbital interaction Vp between adatom and surface cation, the difference ΔEd in the self-energies of a surface cation and a bulk one, and the local perturbation ΔW0 on the self-energy of the surface cation that participated in the chemisorption bond. As a result of chemisorption the oxygen adatom shares the delocalized surface states of the perovskite, and in addition to that two peaks appear next to the surface states, one below the surface band being a bonding state and one above it, being an antibonding state. The change in chemisorption energy with the adatom-surface interaction strength has been investigated.