Elektronik ve Haberleşme Mühendisliği Bölümü Yayın Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/260
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Article Citation - WoS: 1Citation - Scopus: 1Determination of Chemisorption Probabilities of Hydrogen Molecules on a Nickel Surface by Artificial Neural Network(Croatian Chemical Soc, 2008) Güvenç, Ziya Burhanettin; Boeyuekata, Mustafa; Kocyigit, Yuecel; Guevenc, Ziya B.; Böyükata, Mustafa; Bilgisayar MühendisliğiDissociative chemisorption probabilities for H-2(v, j) + Ni(100) collision systems have been estimated by using Artificial Neural Network (ANN). For training, previously determined probability values via molecular dynamics simulations have been used. Performance of the ANN, for predicting any quantities in the molecule-surface interaction, has been investigated. Effects of the surface sites and the rovibrational states of the molecule on the process are analyzed. The results are in good agreement with the related previous studies.Article Citation - WoS: 1Citation - Scopus: 1Structures and Energetics of Cu21-Cu71 Clusters: a Molecular Dynamics Study(Gazi Univ, 2009) Güvenç, Ziya Burhanettin; Cetin, Saime Sebnem; Ozcelik, Suleyman; Guvenc, Ziya B.; Bilgisayar MühendisliğiUsing Molecular Dynamics and thermal quenching simulations the stable geometrical structures and energies of Cun (n=21-71) clusters are identified. The interaction between the cluster atoms is modeled by an EmbeddedAtom Potential Surface, Voter and Chen's version. The stable geometrical structures and energies are obtained from 500 phase space coordinates generated along high-energy trajectories. The internal energy (about T=2500 K) is above the melting temperature of the Cun clusters. The thermal quenching technique is employed to remove slowly the internal kinetic energy of the clusters. Because of this slow minimization process the locally stable isomers are separated from those meta-stable ones.Conference Object Citation - WoS: 3Citation - Scopus: 5Reactivity of the Nin(T) (N=54,55,56) Clusters With D2(V,j) Molecule: Molecular Dynamics Simulations(Elsevier Science Bv, 2004) Özçelik, S; Güvenç, ZB; Durmus, P; Jellinek, JThe reactive channel of the D(2) (v, j) + Ni(n) (T) (n = 54, 55, 56) collision system is studied via quasiclassical molecular dynamics simulations. The cluster is described using an embedded-atom potential, and the interaction between the molecule and the cluster is modeled by a LEPS (London-Eyring-Polanyi-Sato) potential energy function. Dissociative chemisorption probabilities are computed as functions of the impact parameter and the collision energy, and are used to evaluate the reaction cross-sections. Effects of the initial rovibrational states of the molecule and the temperatures of the clusters on the reactive channel are analyzed. Reaction rate constants are also computed and compared with those measured experimentally. (C) 2004 Elsevier B.V. All rights reserved.Article Citation - WoS: 7Citation - Scopus: 7Structure and Dynamical Properties of Aun, N=12-14 Clusters: Molecular Dynamics Simulation(World Scientific Publ Co Pte Ltd, 2005) Yildirim, EK; Atis, M; Güvenç, ZBUsing molecular dynamics and thermal quenching methods on the basis of Voter-Chen version of the embedded-atom method, we have studied the melting behavior of Au-N (N = 12, 13, 14) clusters. This behavior is described in terms of overall and atom resolved root-mean-square bond-length fluctuations, specific-heat, short- and long-time average coordination numbers of each atom and short-time average temperatures of the clusters. The isomer sampling probabilities are obtained from the thermal quenching of the molten clusters, and their energy-spectrum widths are investigated. Phase change of a cluster takes place with the collective and simultaneous motion of all the atoms.Article Citation - WoS: 7Citation - Scopus: 8Molecule-Surface Interaction: Dissociative Chemisorption of a D2 (V=0, J=0) Molecule on Rigid Low Index Ni Surfaces(Elsevier Science Bv, 2004) Böyükata, M; Güvenç, ZBD(2) + Ni-surface collision system has been studied by a quasiclassical molecular dynamic simulation method. Dissociative adsorption of a D(2) molecule on rigid Ni(1 0 0), Ni(1 1 0) and Ni(1 1 1) surfaces are investigated. Interactions between the molecule and Ni surfaces were described by a LEPS potential. The contour plots of the LEPS function is presented as functions of the distances between the center of mass of the D(2) and surface, and between the two deuterium atoms (D-D) for topologically different sites of the surfaces. Dissociative chemisorption probabilities of the D(2) (nu = 0, j = 0) molecule on various sites of the surfaces are presented for different translation energies between 0.001 and 1.0 eV. The probabilities obtained at each collision site have unique behavior. At low collision energies indirect processes enhance the reactivity. The results are compared with the available studies. The physical mechanisms underlying the results are discussed. (C) 2004 Elsevier B.V. All rights reserved.Article Citation - WoS: 6Citation - Scopus: 7Bombardment of Ni(100) Surface With Low-Energy Argons: Molecular Dynamics Simulations(Elsevier Science Sa, 2005) Güvenç, ZB; Hippler, R; Jackson, BResults of molecular dynamics simulations of the sputtering of Ni(100) by Ar atoms are reported. The solid is described by an embedded atom potential, and the interaction between the projectile and the metal atoms is modelled by a Morse-like function. Processes leading to Ni atom emissions from the lattice are analysed over the energy range of 70-80 eV In this energy range cluster (larger than three atoms) emission is not observed. The maximum penetration depth of Ar, the kinetic energy and angular distributions of the reflected Ar, and the sputtered Ni atoms are evaluated as functions of the impact energy and sputtering time. The computed sputtering yield is compared with the available theoretical and experimental data. (C) 2004 Elsevier B.V. All rights reserved.Conference Object Citation - WoS: 14Citation - Scopus: 13Structures and Energetics of Pd21-Pd55 Clusters(Elsevier Science Bv, 2003) Karabacak, M; Özçelik, S; Güvenç, ZBUsing molecular dynamics and thermal quenching simulations the stable geometrical structures and energies of Pd-n (n = 21-55) clusters are identified. The interaction between the cluster atoms is modeled by an embedded-atom (EA) potential energy surface, Voter and Chen's version. The stable geometrical structures and their minimum energies are obtained from 500 phase space coordinates generated along high-energy trajectories. The internal energies (about T = 2500 K) are above the melting temperature of the Pd-n clusters. The thermal quenching technique is employed to remove slowly the internal kinetic energy of the clusters. Because of this slow minimization process the locally stable isomers are separated from those meta-stable ones. Stability of the clusters is examined by the first and the second energy differences. The average bond lengths are obtained and analyzed as a function of the size of the clusters. (C) 2003 Elsevier Science B.V. All rights reserved.Conference Object Citation - WoS: 30Citation - Scopus: 31Structures and Melting of Cun (N=13, 14, 19, 55, 56) Clusters(Elsevier Science Bv, 2003) Özçelik, S; Güvenç, ZBConstant-energy molecular dynamics simulation was utilized to study the most stable geometrical structures, binding energy, melting, phase changes of Cu-n (n = 13, 14, 19, 55, 56) clusters. These sizes form shell and near shell structures. The cohesion of clusters is modeled by an embedded-atom potential, which contains many-body atomic interaction terms. Phase space coordinates which are generated along high-energy trajectories are used as the initial configurations (500 independent configurations) for thermal quenching in order to obtain the most stable isomers. The melting temperatures of the clusters are estimated. The melting-like transition is described in terms of relative root-mean-square bond-length fluctuations, specific heats, and caloric curves. (C) 2003 Elsevier Science B.V. All rights reserved.Article Citation - WoS: 3Citation - Scopus: 3Parallelization of a Molecular Dynamics Simulation of an Ion-Surface Collision(World Scientific Publ Co Pte Ltd, 2005) Özdogan, C; Güvenç, ZB; Atis, MParallel molecular dynamics simulation study of the ion-surface collision system is reported. A sequential molecular dynamics simulation program is converted into a parallel code utilizing the concept of parallel virtual machine (PVM). An effective and favorable algorithm is developed. Our parallelization of the algorithm shows that it is more efficient because of the optimal pair listing, linear scaling, and constant behavior of the internode communications. The code is tested in a distributed memory system consisting of a cluster of eight PCs that run under Linux (Debian 2.4.20 kernel). Our results on the collision system are discussed based on the speed up, efficiency and the system size. Furthermore, the code is used for a full simulation of the Ar-Ni(100) collision system and calculated physical quantities are presented.Conference Object Citation - WoS: 36Citation - Scopus: 30Structures and Energetics of Pdn (n=2-20) Clusters Using an Embedded-Atom Model Potential(Elsevier Science Bv, 2002) Karabacak, M; Özçelik, S; Güvenç, ZBWe have studied the structure and energetics of the stable isomers of Pd(n) (n = 2-20) clusters by using molecular dynamics and slow-quenching techniques. Cohesion of the clusters is modeled by an embedded-atom potential due to Voter and Chen, which contains many-body atomic interactions. The isomers' statistics are obtained from 10000 independent initial configurations, which have been generated along a high-energy trajectory (the chosen energy value is high enough to melt the cluster). The internal kinetic energy of these initial conditions is removed slowly. Because of this slow minimization process the locally stable isomers are separated from those meta-stable ones. Probabilities belonging to sampling the basins of attractions of each isomer are computed, and compared with each other. Furthermore, the spectrum, which is formed by isomers' energies, is analyzed. (C) 2002 Published by Elsevier Science B.V.