Browsing by Author "Güvenç, Ziya B."

Now showing 1 - 6 of 6

Effects of molecular rovibrational states and surface topologies for molecule-surface interaction: Chemisorption dynamics of D(2) collision with rigid Ni surfaces
(Springer, 2006) Böyükata, Mustafa; Güvenç, Ziya B.; 120207; 06.01. Bilgisayar Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
A quasiclassical and micro-canonical molecular dynamic simulation techniques have been applied for D(2)(v,j) + Ni-surface collision systems. Dissociative adsorptions of a D(2) molecule on the rigid low index (100), (110) and (111), surfaces of the nickel are investigated to understand the effects of the different surfaces, impact sites and the initial rovibrational states of the molecule on molecule-surface collisions. Interactions between the molecule and the Ni surfaces are mimicked by a LEPS potential. Dissociative chemisorption probabilities of the D(2)(v,j) Molecule ( for the vibrational (v) = 0 and rotational (j) = 0, 1, 3, 10, and for the v = 1,j = 0 states on different impact sites of the surfaces) are presented for the translation energies between 0.001 and 1.0 eV. The probabilities obtained at each collision site have unique behavior for the colliding molecule which is moving along the surface normal direction. It has been observed that at the low collision energies the indirect processes (steering effects) enhance the reactivity on the surfaces. The results are compared to the related studies in the literature.
Hydrogen hosting of nanoscale boron cluster
(Editura Academiei Romane, 2008) Böyükata, Mustafa; Özdoğan, C.; Güvenç, Ziya B.; 40569; 09.01. Ortak Dersler Bölümü; 06.01. Bilgisayar Mühendisliği; 06. Mühendislik Fakültesi; 09. Rektörlük; 01. Çankaya Üniversitesi
In this paper the Density Functional Results of hydrogen bonded boron micro clusters with B3LYP/6-311++G(d,p) level of computations will be presented. Energetics and structural stability with their possible stable geometries of various selected micro complexes of B(m)H(n) (for m and n <= 11 )boron hydrides have been analysed, and their binding energies with HOMO-LUMO energy gaps have been determined. Mainly, erects of the number of hydrogen atoms on the structures of the boranes are assessed. Moreover, for the cage configurations their distortions have been investigated for the neutral, anionic and cationic cases. It has been observed that there have been two opposing factors for the cage configurations. One of which is the "peeling" of the cage structures by the hydrogen atoms, and the other one is reforming a smaller cage form simultaneously with there remaining boron atoms inside. This is observed mostly for the odd values of m. From our studies it has been also observed that with the bare boronclusters alone, it is difficult to increase the capacity of the hydrogen storage. Therefore, further studies are necessary with the boron complexes
MD study of energetics, melting and isomerization of aluminum microclusters
(Springer, 2006) Böyükata, Mustafa; Güvenç, Ziya B.; 120207; 06.01. Bilgisayar Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Voter and Chen version of an Embedded Atom Model has been applied to study the locally stable structures, energies, melting, isomerization and growth patterns of small aluminum clusters, Al(n), in the size range of n = 2 - 13. Using molecular dynamics and thermal quenching simulations, the global minima and the other locally stable structures have been distinguished from those stationary structures that correspond to saddle points of the potential energy surface. A large number (10000) of independent initial configurations generated at high temperatures has been used to obtain the stable isomers, and the probabilities of sampling different basins of attractions, for each size of the clusters. Their energy spectra have been determined and melting, and isomerization dynamics are investigated.
Citation - Scopus: 5
Structural Forms and Energies of NiN, N=12-14, Clusters
(Assoc Sci Res, 1999) Güvenç, Ziya B.; Güvenç, Dilek; Jellinek, Julius; 06.01. Bilgisayar Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Equilibrium structural forms of the $Ni_n$, n=12-14, clusters, as defined by an embedded-atom potential, are obtained using molecular dynamics and thermal quenching simulations. The isomers (locally stable geometric forms) are distinguished from those stationary structures that correspond to saddle points of the potential energy surface. Isomer statistics are obtained using a large number of initial quenching configurations generated along high-energy trajectories (the energies are high enough to "melt" the clusters). Probabilities of sampling the basins of attraction of the different isomers are computed and the spectra of their energies are analyzed.
Surface modification by 1 keV ion impact: molecular dynamics study of an Ar+-Ni(100) collision system
(2008) Özdoğan, Cem; Atis, Murat; Güvenç, Ziya B.; 40569; 09.01. Ortak Dersler Bölümü; 06.01. Bilgisayar Mühendisliği; 06. Mühendislik Fakültesi; 09. Rektörlük; 01. Çankaya Üniversitesi
An Ar+-Ni(1 0 0) collision system at 1 keV impact energy was investigated by using realistic isoenergetic molecular dynamics (MD) simulations. The sputtering process upon Ar+ ion impact and damage to the Ni(1 0 0) surface are examined in detail. Studying of high bombarding energy regions leads to the necessity of larger and thick enough slabs, otherwise incoming ions can easily pass through the slab; as a result, investigated physical properties may not be revealed. In addition the simulation time should be long enough to observe and to calculate a reliable macroscopic property such as sputtering yield that is addressed in this study. In order to preserve the total energy in the simulation at this collision energy a small time-step (0.1 fs) is used. We have made use of our developed linear scaling parallel MD program to overcome these demands. The Ni(1 0 0) slab is formed by 63700 atoms (122 angstrom x 122 angstrom x 44 angstrom) and the total observation time for each collision event is about 2.25 ps. Several properties such as penetration depths, angular and energy distributions of the reflected Ar and sputtered Ni atoms as well as dissociation time, embedded, scattering, sputtering patterns and geometries of the sputtered clusters are also reported, and the calculated sputtering yield is found to be in good agreement with the available experimental results.
Temiz Enerji Kaynağı Hidrojenin Nano Yapılarda Depolanması
(2007) Büyükata, Mustafa; Atiş, Murat; Güvenç, Ziya B.; Özdoğan, Cem; 01. Çankaya Üniversitesi