Browsing by Author "Sebetci, A"

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Citation - WoS: 73
Citation - Scopus: 69
Energetics and Structures of Small Clusters: Ptn, N=2-21
(Elsevier, 2003) Sebetci, A; Güvenç, ZB; 05.01. İç Mimarlık; 06.01. Bilgisayar Mühendisliği; 06. Mühendislik Fakültesi; 05. Mimarlık Fakültesi; 01. Çankaya Üniversitesi
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.
Citation - WoS: 19
Citation - Scopus: 19
Global Minima for Free Ptn Clusters (n=22-56): a Comparison Between the Searches With a Molecular Dynamics Approach and a Basin-Hopping Algorithm
(Springer, 2004) Sebetci, A; Güvenç, ZB; 05.01. İç Mimarlık; 06.01. Bilgisayar Mühendisliği; 06. Mühendislik Fakültesi; 05. Mimarlık Fakültesi; 01. Çankaya Üniversitesi
Using molecular dynamics and thermal quenching simulation techniques, and the basin-hopping Monte Carlo algorithm we have studied the global minima and energetics of free Pt-N clusters in the size range of N = 22-56. The clusters have been described by the Voter and Chen version of an embedded-atom model, which is derived by fitting to experimental data of both the diatomic molecule and bulk platinum simultaneously. A comparison between the two search techniques has been performed and it is found that the basin-hopping algorithm is more efficient than a molecular dynamics minimization approach in the investigation of the global minima. The results show that the global minima of the Pt clusters have structures based on either octahedral, decahedral or icosahedral packing. Some of the icosahedral global minima do not have a central atom. The 54-atom icosahedron without a central atom is found to be more stable than the 55-atom complete icosahedron. The resulting structures have been compared with the previous theoretical calculations.
Citation - WoS: 49
Citation - Scopus: 49
Global Minima of Aln, Aun and Ptn, N≤80, Clusters Described by the Voter-Chen Version of Embedded-Atom Potentials
(Iop Publishing Ltd, 2005) Sebetci, A; Güvenç, ZB; 05.01. İç Mimarlık; 06.01. Bilgisayar Mühendisliği; 06. Mühendislik Fakültesi; 05. Mimarlık Fakültesi; 01. Çankaya Üniversitesi
We report the global minima for aluminium, gold and platinum metal clusters modelled by the Voter-Chen version of the embedded-atom model potential containing up to 80 atoms using the basin-hopping Monte Carlo minimization approach. The results show that the global minima of the Al, Au and Pt clusters have structures based on either octahedral, decahedral, icosahedral or a mixture of decahedral and icosahedral packing. The 54-atom icosahedron without a central atom is found to be more stable than the 55-atom complete icosahedron for all of the elements considered in this work. Most of the Al global minima are identified as face-centred cubic structures and many of the An global minima are found to be low symmetric structures, both of which are in agreement with the previous theoretical and experimental Studies. Although many of the Pt global minima are identical with the global minima of the corresponding Au clusters, the most stable sizes of the Pt clusters correspond to the same sizes of the Al clusters.
Citation - WoS: 24
Citation - Scopus: 24
Molecular Dynamics Simulation of the Melting Behaviour of 12-, 13-, 14-Atom Icosahedral Platinum Clusters
(Iop Publishing Ltd, 2004) Sebetci, A; Guvenc, ZB; 05.01. İç Mimarlık; 06.01. Bilgisayar Mühendisliği; 06. Mühendislik Fakültesi; 05. Mimarlık Fakültesi; 01. Çankaya Üniversitesi
Using 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.
Citation - WoS: 4
Citation - Scopus: 4
Phase Changes in Icosahedral 54-, 55-, 56-Atom Platinum Clusters
(World Scientific Publ Co Pte Ltd, 2004) Güvenç, ZB; Kökten, H; Sebetci, A; 05.01. İç Mimarlık; 06.01. Bilgisayar Mühendisliği; 06. Mühendislik Fakültesi; 05. Mimarlık Fakültesi; 01. Çankaya Üniversitesi
Using the Voter and Chen version of an embedded-atom model, derived by fitting simultaneously to experimental data both the diatomic molecule and bulk platinum, we have studied the melting behavior of free, icosahedral, 54-, 55- and 56-atom platinum clusters in the molecular dynamics simulation technique. 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 effect of a central atom in the icosahedral structure to the melting process is discussed. The results show that the global minimum structures of the 54-, 55- and 56-atom Pt clusters do not melt at a specific temperature, rather, melting processes take place over a finite temperature range. The heat capacity peaks are not delta-functions, but instead remain finite. An ensemble of clusters in the melting region is a mixture of solid-like and liquid-like clusters.
Citation - WoS: 9
Citation - Scopus: 11
Thermodynamics of Small Platinum Clusters
(Elsevier Science Bv, 2006) Sebetci, A; Güvenç, ZB; Kökten, H; 20965; 163582; 05.01. İç Mimarlık; 06.01. Bilgisayar Mühendisliği; 06. Mühendislik Fakültesi; 05. Mimarlık Fakültesi; 01. Çankaya Üniversitesi
Using the Voter and Chen version of an embedded atom model, derived by fitting simultaneously to experimental data of both the diatomic molecule and bulk platinum, we have studied the melting behavior of free, small platinum clusters in the size range of N = 15-19 in the molecular dynamics simulation technique. 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 as the Pt-15-Pt-18 clusters exhibit multistage melting, melting in Pt-19 cluster takes place in a single but interesting stage. None of these melting stages occurs at a specific temperature, rather, melting processes take place over a finite temperature range. This range is larger for less symmetric clusters. An ensemble of clusters in the melting region is a mixture of different isomeric forms of the clusters. The multistage melting and the occurrence of a single melting stage over a temperature range are two different phenomena. (c) 2005 Elsevier B.V. All rights reserved.