Elektronik ve Haberleşme Mühendisliği Bölümü Yayın Koleksiyonu

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  • Article
    Citation - WoS: 10
    Citation - Scopus: 9
    Hydrogen Recombination on a Mixed Adsorption Layer at Saturation on a Metal Surface: H→(D+h)sat+ni
    (Elsevier, 2003) Güvenç, ZB; Güvenç, D
    Interactions of H atom beams with (D + H)-covered Ni(1 0 0) surfaces are simulated at saturation level of 0.93 monolayer using quasi-classical microcanonical trajectory method. The Ni substrate is treated as a non-rigid multilayer slab using an embedded-atom method. The model many-body potential energy surface London-Eyring-Polanyi-Sato used to characterize the interactions between H-H and H-Ni(1 0 0) systems parameterized by fitting to the results of detailed total-energy calculations based on density functional theory. Since most of the incident H atoms trap to form hot atoms, reactions between the projectile atom and adsorbates are mainly due to the hot atom process. Results of a linear behavior of the total HD and quadratic behavior of the D-2 yields with the initial D coverage, in addition, significantly low secondary reactions between the adsorbates are found to be in good agreement with the experiment. In addition distributions of the rotational states of the product molecules, molecular desorption angles, vibrational states of the product molecules, molecular formation and desorption time, total and translational energies of the product molecules are also calculated as functions of different H and D coverages on the surface. (C) 2003 Elsevier Science B.V. All rights reserved.
  • Article
    Citation - WoS: 73
    Citation - Scopus: 70
    Energetics and Structures of Small Clusters: Ptn, N=2-21
    (Elsevier, 2003) Sebetci, A; Güvenç, ZB
    The Voter and Chen version of an embedded-atom model, derived by fitting to experimental data of both diatomic molecule and bulk platinum simultaneously, has been applied to study the locally stable structures, energies and growth patterns of small platinum clusters in the size range of N = 2-21. 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. Ten thousand independent initial configurations generated at high temperatures (about 2600 K) were used to obtain the number of isomers and the probabilities of sampling different basins of attractions, for each size of the clusters. Their energy spectra have been analyzed. Comparisons have been made with the results of previous calculations using electronic structure and empirical potential methods. Although many of the lowest energy structures correspond to icosahedral growth, a number of new structures have been identified for N = 15, 16, 17, 18, 20 and 21. It has been found that the lowest energy structures are not always the most probable isomers for each size. (C) 2002 Elsevier Science B.V. All rights reserved.