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: 2Citation - Scopus: 3Diffraction in Time of an Entangled Non-Relativistic Quantum Particle(Iop Publishing Ltd, 2021) Umul, Yusuf ZiyaThe diffraction process of an entangled non-relativistic quantum particle in time domain is investigated. The scenario consists of two entangled spin-0 particles and a quantum shutter, which is opened at an initial time. The particles are traveling in two opposite sides and expressed with a single wave function. The integral solution of the Schrodinger equation is considered for two particles case. The initial condition is expressed in terms of an entangled wave function. The time-diffracted matter wave is obtained in terms of the Fresnel integral. The effect of the phenomenon of diffraction in time is examined numerically for the entangled system of two particles.Article Citation - WoS: 24Citation - Scopus: 24Molecular Dynamics Simulation of the Melting Behaviour of 12-, 13-, 14-Atom Icosahedral Platinum Clusters(Iop Publishing Ltd, 2004) Sebetci, A; Guvenc, ZBUsing the molecular dynamics simulation technique, we have studied the melting behaviour of free, icosahedral Pt-N clusters in the size range of N = 12-14. The Voter and Chen version of an embedded-atom model, derived by fitting to experimental data of both the diatomic molecule and bulk platinum simultaneously, has been employed in this study. 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 results show that while the 13-atom icosahedron and the 12-atom cluster with a vacancy on the icosahedral surface exhibit one-stage melting, the 14-atom cluster with an adatom on the icosahedral surface undergoes two-stage melting, as the temperature increases.Article Citation - WoS: 8Citation - Scopus: 9Effects of Hydrogen Hosting on Cage Structures of Boron Clusters: Density Functional Study of Bmhn (m=5-10 and N ≤ M) Complexes(Iop Publishing Ltd, 2008) Ozdogan, C.; Guvenc, Z. B.; Boyukata, M.; Özdoan, C.The structural stability of hydrogen bonded boron microclusters has been studied by using the density functional theory. Effects of the increasing number of hydrogen atoms on the cage geometries of B-5-B-10 clusters, and the distortion of the cage configurations of the boranes are assessed. The possible stable structures of BmHn(m = 5-10 and n <= m) boron hydrides, their binding energies, HOMO-LUMO energy gaps and the total atomic charges of the B-m in the complexes are determined. For the series of B5Hn, B7Hn, and B9Hn major structural changes are observed.Article Citation - Scopus: 1Surface Modification by 1 Kev Ion Impact: Molecular Dynamics Study of an Ar<sup>+</Sup>-ni(100) Collision System(Iop Publishing Ltd, 2008) Atis, Murat; Guvenc, Ziya B.; Ozdogan, CemAn 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: 16Citation - Scopus: 16Molecular Dynamics Simulation of Melting Behaviour of Small Gold Clusters: Aun (n=12-14)(Iop Publishing Ltd, 2007) Yildirim, E. K.; Atis, M.; Guvenc, Z. B.We have investigated the melting behaviour of AuN (N = 12 - 14) clusters by means of molecular dynamics simulation on the basis of the Voter - Chen version of the embedded-atom method. The melting behaviour of the clusters is described in terms of short-time average temperatures and atomic coordination numbers of the clusters. Results have shown that during the melting process, the phase changes occur as a collective and simultaneous motion of all the atoms in a very short-time interval. Furthermore the Au-14 cluster presents a two-stage melting behaviour which is different from those of the Au-12 and Au-13 clusters. The isomer sampling probabilities are obtained from the thermal quenching of the molten clusters, and their energy-spectrum widths are investigated. The results of the isomer forming probabilities showed that the global minimum structures of these clusters are not always the most probable ones to be formed in the experiments.Article Citation - WoS: 9Citation - Scopus: 10Structures and Melting of Agn (N = 7, 12-14) Clusters(Iop Publishing Ltd, 2005) Atis, M; Aktas, H; Güvenç, ZBWe have studied the most stable structures of Ag-N (N = 7, 12, 13, 14) clusters and investigated their binding energies and melting behaviours using molecular dynamics and thermal quenching methods based on the Voter-Chen version of the embedded atom method. The melting like transition is described in terms of atom resolved root-mean-square bond length fluctuations, specific heats, coordination numbers and short-time averaged temperatures. Some of these diagnostic tools are also used for the overall behaviour of the clusters. The results are compared with the relevant literature.Article Citation - WoS: 18Citation - Scopus: 18Differences in Melting Behaviours of Disordered and Symmetric Clusters: Aun(n=54-56)(Iop Publishing Ltd, 2006) Yildirim, E. K.; Guvenc, Z. B.We have investigated the melting behaviours of disordered and symmetric gold clusters (Au-N, N = 54 - 56) by means of molecular dynamics simulations. We have found that there is no single isolated lowest energy structure for this size of Au clusters. Instead there are many nearly degenerate disordered low lying structures. The melting behaviours of these disordered structures showed that the melting occurs as a gradual process in which initially, behaviours of the surface and the inner atoms are quite different from each other, and they do not mix until the beginning of the melting. On the other hand, the symmetric forms of the Au-N ( N = 54 - 56) present different melting behaviours from those of the corresponding disordered structures. Their melting occurs suddenly, i.e. over a very short temperature interval. During the heating of these symmetric forms no phase changes occur until the melting temperature at which melting occurs as a collective motion of all the atoms in the cluster. On the other hand, the phase changes in the disordered structures take place as a result of both collective motions of all the atoms in the cluster, and as local displacements of the atoms.