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Öğe Ab initio search for global minimum structures of neutral and anionic hydrogenated Li-5 clusters(Elsevier Science Bv, 2013) Muz, Iskender; Atis, Murat; Canko, Osman; Yildirim, Erdem KamilThe structure and some electronic properties of neutral and anionic Li5Hn (n = 0-6) clusters have been studied by using the stochastic search method with the B3LYP/6-31G level of theory. After searching possible isomers, first few isomers with the lowest energy have been recalculated by the B3LYP/6-311G++(2d,2p) and CCSD(T)/6-311G++(2d, 2p) level of theory. The method used in this study has been compared with the previously reported ab initio calculations, and its reliability has been confirmed. The anionic Li5Hn (n = 0-6) clusters are reported in this study for the first time. Our results show that in general, stability increases with increasing number of hydrogen atoms. The fragmentation energies of hydrogenated Li-5 clusters are easier to fragmentation the two hydrogen atoms than one hydrogen atom in hydrogenated clusters, and it is too high for the reversible hydrogen storage systems. (C) 2013 Elsevier B.V. All rights reserved.Öğe Search for the Global Minimum Structures of AlB3H2n (n=0-6) Clusters(Wiley-Blackwell, 2015) Muz, Iskender; Canko, Osman; Atis, Murat; Yildirim, Erdem KamilThe global minimum structures of AlB3H2n (n=0-6) clusters are determined using the stochastic search method at the B3LYP/6-31G level of theory. These initially specified geometries are recalculated using B3LYP and CCSD(T) methods using the 6-311++G(**) basis set. The structural and electronic properties of the two lowest-lying isomers are presented. The structural parameters obtained for aluminum borohydride are compared with the experimental and theoretical results. The H-2 fragmentation energies of the most stable isomers are investigated. Chemical bonding analyses for the global minimum of AlB3H2n (n=0-6) clusters are performed using the adaptive natural density partitioning method. (c) 2014 Wiley Periodicals, Inc.Öğe Structural and computational characterization of 4 ',4 ',6 ',6 '-tetrachloro-3-(2-methoxyethyl)-3H,4H-spiro-1,3,2-benzoxaza phosphinine-2,2 '-[1,3,5,2,4,6]triazatriphosphinine(Elsevier, 2016) Isiklan, Muhammet; Yildirim, Erdem Kamil; Atis, Murat; Sonkaya, Omer; Cosut, BunyeminIn this study a new monospirocyclic phosphazene derivative, 4',4',6',6'-tetrachloro-3-(2-methoxyethyl)3H,4H-spiro [1,3,2-benzoxazaphosphinine-2,2'- [1,3,5,2,4,6] triazatriphosphinine] (SP1) was synthesized from the reaction of hexachlorocyclotriphosphazene (N3P3CI6) with N/0 donor-type, 2-{[(2-Metoxyethyl) amino]methylphenol. The structural investigations of the compound were verified by elemental analyses, MS, FFIR, 1H, 13C, 11 --P NMR spectroscopy and the single crystal X-ray diffraction analysis. The structural and spectroscopic data of the molecule in the ground state were calculated by using density functional method (DFT) using 6-311++G (d, p) basis set. The complete assignments of all vibrational modes were performed on the basis of the total energy distributions (TED). Isotropic chemical shifts (31P, 1H and 13C NMR) were calculated using the gauge-invariant atomic orbital (GIAO) method. Theoretical calculations of bond parameters, harmonic vibration frequencies and nuclear magnetic resonance are in good agreement with experimental results. The electrophilic and nucleophilic attack centers in SP1 were predicted with the local softness values (sit, and si) of individual atoms and it is confirmed that P atoms of the PCl2 groups are nucleophilic attack centers. (C) 2016 Elsevier B.V. All rights reserved.Öğe Structure and dynamical properties of Au-N, N=12-14 clusters: Molecular dynamics simulation(World Scientific Publ Co Pte Ltd, 2005) Yıldırım, Erdem Kamil; Atis, Murat; Güvenç, Ziya B.Using 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.Öğe Structure and Energetic of Bn (n = 2–12) Clusters: Electronic Structure Calculations(Wiley, 2007) Atis, Murat; Özdoğan, Cem; 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.
