arXiv subjects

Ali Sebetci

Publications and source records attributed to Ali Sebetci.

5 recordsLinked to original sources

arXiv2009

Structural, Magnetic, and Electronic Properties of the Monometallofullerene Gd@C_82 : Theory

The structural, electronic, and magnetic properties of Gd@C_82 endohedral metallofullerene have been studied by employing on-site correlation corrected, scalar-relativistic and full-relativistic density functional theory within the local density and generalized gradient approximations. The experimentally observed reduction of the magnetic moment of Gd@C_82 with respect to that of a free Gd^+3 ion can be explained by a tiny hybridization between unoccupied Gd-4f states and carbon-pi states, resulting in a generic antiferromagnetic coupling of the Gd-4f spin with the remaining unpaired spin in the hybridized molecular orbital.

physics.atm-clus↗

arXiv2008

Does Spin-Orbit Coupling Effect Favor Planar Structures for Small Platinum Clusters?

We have performed full-relativistic density functional theory calculations to study the geometry and binding energy of different isomers of free platinum clusters Pt$_{n}$ ($n=4-6$) within the spin multiplicities from singlet to nonet. The spin-orbit coupling effect has been discussed for the minimum-energy structures, relative stabilities, vibrational frequencies, magnetic moments, and the highest occupied and lowest unoccupied molecular-orbital gaps. It is found in contrast to some of the previous calculations that 3-dimentional configurations are still lowest energy structures of these clusters, although spin-orbit effect makes some planar or quasi-planar geometries more stable than some other 3-dimentional isomers.

physics.atm-clus↗

arXiv2006

A Density Functional Study of Bare and Hydrogenated Platinum Clusters

We perform density functional theory calculations using Gaussian atomic-orbital methods within the generalized gradient approximation for the exchange and correlation to study the interactions in the bare and hydrogenated platinum clusters. The minimum-energy structures, binding energies, relative stabilities, vibrational frequencies and the highest occupied and lowest unoccupied molecular-orbital gaps of Pt_nH_m (n=1-5, m=0-2) clusters are calculated and compared with previously studied pure platinum and hydrogenated platinum clusters. We investigate any magic behavior in hydrogenated platinum clusters and find that Pt_4H_2 is more stable than its neighboring sizes. Our results do not agree with a previous conclusion that 3D geometries of Pt tetramer and pentamer are unfavored. On the contrary, the lowest energy structure of Pt_4 is found to be a distorted tetrahedron and that of Pt_5 is found to be a bridge site capped tetrahedron which is a new global minimum for Pt_5 cluster. The successive addition of H atoms to Pt_n clusters leads to an oscillatory change in the magnetic moment of Pt_3 - Pt_5 clusters.

physics.atm-clus↗

arXiv2004

Global minima of Al_N, Au_N and Pt_N, N=2-80, clusters described by Voter-Chen version of embedded-atom potentials

Using the basin-hopping Monte Carlo minimization approach 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. The virtue of the Voter-Chen potentials is that they are derived by fitting to experimental data of both diatomic molecules and bulk metals simultaneously. Therefore, it may be more appropriate for a wide range of the size of the clusters. This is important since almost all properties of the small clusters are size dependent. 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. The most of the Al global minima are identified as some fcc structures and many of the Au global minima are found to be some low symmetric structures, which are both in agreement with the previous experimental studies.

physics.atm-clus↗

arXiv2003

Molecular Dynamics Simulation of the Melting Behaviours of 12-, 13-, 14-Atom Icosahedral Platinum Clusters

Using molecular dynamics simulation technique, we have studied the melting behaviours of free, icosahedral PtN clusters in the size range of N=12-14. 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 employed in the 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 13-atom icosahedron and 12-atom cluster with a vacancy on the icosahedral surface exhibit one-stage melting, 14-atom cluster with an adatom on the icosahedral surface undergoes two-stage melting, as the temperature increases.

physics.atm-clus↗