Bilgisayar Mühendisliği Bölümü Yayın Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/253
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Article Surface modification by 1 keV ion impact: molecular dynamics study of an Ar+-Ni(100) collision system(IOP Publishing Ltd, 2008) Özdoğan, Cem; Atis, Murat; Güvenç, Ziya B.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.Article Citation - WoS: 53Citation - Scopus: 61Structure and Energetic of Bn (n=2-12) Clusters: Electronic Structure Calculations(Wiley, 2007) Oezdogan, Cem; Guevenc, Ziya B.; Atis, Murat; Özdoǧan, Cen; Güvenç, Ziya B.The electronic and geometric structures, total and binding energies, first and second energy differences, harmonic frequencies, point symmetries, and highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps of small and neutral B-n (n = 2-12) clusters have been investigated using density functional theory (DFT), B3LYP with 6-311 + + G(d,p) basis set. Linear, planar, convex, quasi-planar, three-dimensional (3D) cage, and open-cage structures have been found. None of the lowest energy structures and their isomers has an inner atom; i.e., all the atoms are positioned at the surface. Within this size range, the planar and quasi-planar (convex) structures have the lowest energies. The first and the second energy differences are used to obtain the most stable sizes. A simple growth path is also discussed with the studied sizes and isomers. The results have been compared with previously available theoretical and experimental works. (C) 2006 Wiley Periodicals, Inc.