Papers by narges sadeghpour
An asymmetry index (AI) is introduced to measure deviation of the electron density distribution i... more An asymmetry index (AI) is introduced to measure deviation of the electron density distribution in a molecule from any given symmetry. This AI is calculated by summing all point-wise differences between electron density distributions before and after symmetry operation. A minimum asymmetry index (MAI) rule is also introduced to evaluate uniquely the extent of asymmetry of a molecule with respect to any reference symmetry operation. This MAI rule prescribes where to locate the reference element of symmetry. The overall MAI for a given molecule with respect to a certain symmetry point group is calculated by averaging over AIs of all symmetry elements appearing in its character table. The proposed AI and the MAI rule are used to measure electron density asymmetry of the NX3, NX2Y/NXY2 and NXYZ (X, Y, Z = H, F, Cl, Br) series of molecules referenced to the C3V symmetry.
Deep eutectic solvents based on L-Arginine and glutamic acid as green catalysts and conductive agents for epoxy resins
Journal of Molecular Liquids, 2021
Abstract Many engineered epoxy products in thee recent years require sustainable materials to be ... more Abstract Many engineered epoxy products in thee recent years require sustainable materials to be contributive in the coming decades. The efficiency of [DES]Arg/Eg and [DES]Glu/Eg deep eutectic solvents (DESs) on the curing reaction of bisphenol A diglicydyl ether (DGEBA) with the application of differential scanning calorimetry (DSC) at temperatures 313-333 K is assessed., The both DESs studied here can act as the catalyst of epoxy-amine reaction, hardener and conducting agents in a simultaneous manner. Moreover, it reveals different reaction kinetics which strongly depend on the type of hydrogen bonding acceptor of the mixture. It is observed that there exist many fundamental differences between the progress of isothermal curing reaction in the presence of [DES]Arg/Eg and [DES]Glu/Eg considering the conductive ionic liquids and non-conductive conventional hardeners. The [DES]Glu/Eg at lower concentrations exhibits different catalytic behavior in the initial stages of the reaction, in a sense that the reaction progresses at higher rates up to 5 min and hampered afterward. In contrast, [DES]Arg/Eg act as a high-efficient catalyst in a sense that it allows the curing reaction approaches the completion level within 30 minutes which is comparable to previously reported conducting dopants. From kinetic results it is deduced that the mechanism of curing reaction follows the first-order kinetic in presence of [DES]Arg/Eg and [DES]Glu/Eg and reaction occurring in presence of [DES]Glu/Eg is characterized by higher activation energy compared to [DES]Arg/Eg. To analyze the efficiency of DESs as a catalyst for the epoxy-amine reaction, a computational study is run on a simplified model reaction catalyzed by [DES]Glu/Eg revealing a significant decrease in activation energy of the catalyzed reaction.
Zeitschrift für Naturforschung A, 2017
First principle density functional theory methods, local density and Perdew-Burke-Ernzerhof gener... more First principle density functional theory methods, local density and Perdew-Burke-Ernzerhof generalized gradient approximations with Goedecker pseudopotential (LDA-G & PBE-G), are used to study the electric field effects on the binding energy and atomic charges of bilayer graphene (BLG) at the Γ point of the Brillouin zone based on two types of unit cells (α and β) containing
Importance of Unit Cells in Accurate Evaluation of the Characteristics of Graphene
Zeitschrift für Naturforschung A, 2016
Effects of the size of the unit cell on energy, atomic charges, and phonon frequencies of graphen... more Effects of the size of the unit cell on energy, atomic charges, and phonon frequencies of graphene at the Γ point of the Brillouin zone are studied in the absence and presence of an electric field using density functional theory (DFT) methods (LDA and DFT-PBE functionals with Goedecker–Teter–Hutter (GTH) and Troullier–Martins (TM) norm-conserving pseudopotentials). Two types of unit cells containing nC=4–28 carbon atoms are considered. Results show that stability of graphene increases with increasing size of the unit cell. Energy, atomic charges, and phonon frequencies all converge above nC=24 for all functional-pseudopotentials used. Except for the LDA-GTH calculations, application of an electric field of 0.4 and 0.9 V/nm strengths does not change the trends with the size of the unit cell but instead slightly decreases the binding energy of graphene. Results of this study show that the choice of unit cell size and type is critical for calculation of reliable characteristics of grap...
Importance of Unit Cells in Accurate Evaluation of the Characteristics of Graphene
nano Online, 2017
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Papers by narges sadeghpour