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Ziashahabi A.,Islamic Azad University at Central Tehran | Ghodselahi T.,Institute for Research in Fundamental Sciences | Heidari Saani M.,Semiconductor Component Industry | Heidari Saani M.,Maleke Ashtar University
Journal of Physics and Chemistry of Solids | Year: 2013

Density functional theory (DFT) calculations are carried out to study the electronic, structural stability and Localized Surface Plasmon Resonance (LSPR) properties of copper nano-clusters. These nano-clusters consisted of 14, 38, 62 and 116 atoms. We studied surface charge density and interband-transitions effects on damping and broadening of the surface plasmon resonance absorption spectra. An enhancement in interband-transition energy and a reduction in surface charge density with decrease in the size of clusters are observed. These features result in the damping and broadening of the LSPR absorption spectra. We also study the structural stability and HOMO-LUMO energy gap of copper clusters. The structural stability of nano-clusters reduces by decreasing the size of the clusters. The HOMO-LUMO energy gap is not zero for the clusters with size less than 2 nm which indicates the lack of conduction electrons which are necessary for LSPR absorption. The calculated interband transition energies are in agreement with LSPR absorption data. We also discuss the difference between size dependent LSPR in copper and gold nano-clusters in the experiment based on calculated surface charge density. © 2013 Elsevier Ltd. Source


Ziashahabi A.,Islamic Azad University at Tehran | Ghodselahi T.,Institute for Research in Fundamental Sciences | Heidari Saani M.,Semiconductor Component Industry | Heidari Saani M.,Maleke Ashtar University
Journal of Nanoparticle Research | Year: 2013

Density functional theory (DFT) calculations are carried out to study the electronic, structural, and stability properties of noble metal nanoclusters. Size-dependent properties of copper, silver, and gold nanoclusters are calculated and compared in the size range below 2 nm. Interband transition energy, formation energy, HOMO-LUMO energy gap, and surface charge density properties of the noble metal clusters are investigated. Noble metal nanoclusters that are investigated in this research have a non-zero energy gap, which indicates a non-metallic character. The formation energies decrease by increasing the size of the clusters. The calculated formation energies are compared with bulk experimental cohesive energies. The trend of reduction in formation energy is consistent with experimental results. The calculated interband transition energies of noble metals reduce by increasing the size of the nanoclusters and are in agreement with the experimental results. Finally, we calculate and compare surface charge density of different noble metals. The calculated surface charge density can explain the experimental results of vanishing of localized surface plasmon resonance with decreasing size in the case of copper clusters, with respect to gold clusters for sizes <2 nm. © 2013 Springer Science+Business Media Dordrecht. Source


Shafiei E.,Shiraz University | Zeinali M.,Maleke Ashtar University | Esfahani A.R.N.,Maleke Ashtar University
ISIJ International | Year: 2011

This paper presents a comparative study on the atmospheric corrosion of steel, at two sites, in Iran. Corrosion rate values, time of wetness and the level of pollutants, namely of SO2 and chlorides, in both atmospheres, were determined for the first year of exposure in order to establish the aggressiveness of the atmospheres. The results obeyed well with the empirical kinetics equation of the form C=Ktn. © 2011 ISIJ. Source

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