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Rad A.S.,Islamic Azad University at Qaemshahr
Applied Surface Science | Year: 2015

We studied the first principles adsorption phenomena of nitrogen dioxide (NO2) and nitrous oxide (N2O) molecules on the surface of pristine graphene and Al-doped graphene using density functional theory (DFT) calculations. The adsorption energies have been calculated for different possible configurations of the molecules on the surface of pristine and Al-doped graphene. Our calculations reveal that the Al-doped graphene has significant adsorption energy, elevated net charge transferring values and smaller bond distances to gases than that of pristine graphene because of the chemical interaction of the mentioned molecules. Furthermore, the calculated density of states (DOS) show the existing of noteworthy orbital hybridization between NO2 as well as N2O and Al-doped graphene during adsorption process which is proving to strong interaction while there is no evidence for hybridization between the those molecules and the pristine graphene. Our calculated adsorption energies for the most stable states for NO2 and N2O was -62.2 kJ mol-1 (-48.5 kJ mol-1 BSSE corrected energy) and -33.9 kJ mol-1 (-22.7 kJ mol-1 corrected energy), which are correspond to chemisorption process. These results point to the suitability of Al-doped graphene as a powerful sensor for practical applications. © 2015 Elsevier B.V. All rights reserved. Source


Ebrahimnejad A.,Islamic Azad University at Qaemshahr
Applied Soft Computing Journal | Year: 2014

In a recent paper, Kaur and Kumar (2012) proposed a new method based on ranking function for solving fuzzy transportation problem (FTP) by assuming that the values of transportation costs are represented by generalized trapezoidal fuzzy numbers. Here it is shown that once the ranking function is chosen, the FTP is converted into crisp one, which is easily solved by the standard transportation algorithms. The main contribution here is the reduction of the computational complexity of the existing method. By solving two application examples, it is shown that it is possible to find a same optimal solution without solving any FTP. Since the proposed approach is based on classical approach it is very easy to understand and to apply on real life transportation problems for the decision makers. © 2014 Elsevier B.V. Source


Rad A.S.,Islamic Azad University at Qaemshahr
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2016

The adsorption energies and orientation of single alcohol molecule (methanol and ethanol) on the surface of Pt-decorated graphene (PtG) were determined from first-principles density functional (DFT) calculations. We found the same adsorption energies as well as connecting distances upon adsorption of MeOH and EtOH on PtG surface, in which at their relaxed structures, the O atom of alcohol is closed to the Pt of PtG surface. We found high adsorption energies, low connecting distances, and high orbital hybridizing upon adsorption of EtOH and MeOH molecules on PtG surface. There are significant shifts in the location of both the HOMO and LUMO, in addition to variation in the charge transfer when the MeOH and EtOH are adsorbed on PtG surface. © 2016 Elsevier B.V. All rights reserved. Source


Shokuhi Rad A.,Islamic Azad University at Qaemshahr
Journal of Alloys and Compounds | Year: 2016

We used first principles density functional theory (DFT) to study the adsorption of mercaptopyridine molecule (as an important intermediate) on the surface of pristine as well as Al- and B-doped graphene sheets. Different possible configurations have been considered for adsorption on both sheets. The resulted electronic structure of each adsorbed system is noticeably different. Our results revealed very weak adsorption on the surface of pristine graphene while relatively high adsorption was achieved by using Al-doped graphene at proper configuration. The adsorption on the surface of B-doped graphene is considerable at proper configuration but is lower than that of Al-doped graphene. Furthermore we analyzed the parameters of electronic structures, the net charge transfer, and orbital analyses including the HOMO-LUMO distributions and also density of states (DOSs) for all possible configurations. As a result, we introduce Al- and B-doped graphenes as hopeful surfaces for adsorption of MP molecule for different purpose. © 2016 Elsevier B.V. All rights reserved. Source


Rad A.S.,Islamic Azad University at Qaemshahr
Surface Science | Year: 2016

We have studied the electronic structure and property of pristine as well as Al-doped graphene sheets towards adsorption of some halomethane compounds (trichloromethane, dichloromethane, and difluoromethane) using density functional theory (DFhsT) calculations. The adsorption energies have been calculated for each adsorbed-adsorbent system. Based on our results, compared to pristine graphene, the Al-doped graphene causes significant adsorption energy, higher charge transferring, and smaller bond distances to halomethane compounds. Our calculated adsorption energies of trichloromethane, dichloromethane, and difluoromethane on Al-doped graphene were - 54.1, - 68.3, and - 123.2 kJ mol- 1, respectively, which are categorized in the chemisorption region while the adsorption of these molecules on pristine graphene release insignificant energies which correspond to very weak adsorption on it. Furthermore, we used charge transfer analysis to search the amount of electron allocation. Orbital analysis including the density of states (DOS) was done to find the possible orbital hybridization between adsorbates and two graphene sheets. These results imply the suitability of Al-doped graphene as a good adsorbent/sensor for halomethane compounds. © 2015 Elsevier B.V. All rights reserved. Source

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