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density-functional-theory
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The effect of structural defects on the electron transport of MoS 2 nanoribbons based on density functional theory
, Article Journal of Theoretical and Applied Physics ; Volume 13, Issue 1 , 2019 , Pages 55-62 ; 22517227 (ISSN) ; Fathipour, M ; Faez, R ; Darvish, G ; Sharif University of Technology
SpringerOpen
2019
Abstract
Using non-equilibrium Green’s function method and density functional theory, we study the effect of line structural defects on the electron transport of zigzag molybdenum disulfide (MoS 2 ) nanoribbons. Here, the various types of non-stoichiometric line defects greatly affect the electron conductance of MoS 2 nanoribbons. Although such defects would be lead to the electron scattering, they can increase the transmission of charge carriers by creating new channels. In addition, the presence of S bridge defect in the zigzag MoS 2 nanoribbon leads to more the transmission of charge carriers in comparison with the Mo–Mo bond defect. Also, we find that the different atomic orbitals and their...
Ab initio study of AMBO3 (A = Li, Na and M = Mn, Fe, Co, Ni) as cathode materials for Li-ion and Na-Ion batteries
, Article ACS Omega ; Volume 5, Issue 15 , April , 2020 , Pages 8952-8961 ; Hafizi Barjini, M ; Momeni, M ; Sharif University of Technology
American Chemical Society
2020
Abstract
According to the importance of polyanion cathode materials in intercalation batteries, they may play a significant role in energy-storage systems. Here, evaluations of LiMBO3 and NaMBO3 (M = Mn, Fe, Co, Ni) as cathode materials of Li-ion and Na-ion batteries, respectively, are performed in the density functional theory (DFT) framework. The structural properties, structural stability after deintercalation, cell voltage, electrical conductivity, and rate capability of the cathodes are assessed. As a result, Li compounds have more structural stability and energy density than Na compounds in the C2/c frame structure. Cell voltage is increased by increasing the atomic number of the transition...
Conversion of a weak organic acid to a super acid in the gas phase
, Article Journal of Physical Organic Chemistry ; Volume 21, Issue 2 , 2008 , Pages 112-118 ; 08943230 (ISSN) ; Tavasoli, E ; Sharif University of Technology
2008
Abstract
The effects of selected metal ions on the gas-phase acidity of weak organic acids have been explored using the DFT and Moller-Plesset Perturbation Theory (MP2) calculations. The three organic acids selected for this study were acetic acid (aliphatic), benzoic acid (aromatic), and glycine (amino acid). The acidities of these compounds are compared with the acidity of their Li +-, Na+-, and K+ -complexed species. The results indicate that upon complexation with Li+, Na+, and K+ at 298K, the gas-phase acidity of acetic acid, for example, varies from 345.3 to 218.8, 230.2, and 240.1 kcal/mol, respectively (i.e., its dissociation becomes much less endothermic). These values indicate that a weak...
MgB2 under pressure and plane strain: a DFT study
, Article Computer Physics Communications ; Volume 179, Issue 6 , 15 September , 2008 , Pages 385-390 ; 00104655 (ISSN) ; Tavana, A ; Akhavan, M ; Sharif University of Technology
2008
Abstract
Full potential density functional theory (DFT) calculations have been performed for the MgB2 superconductor. Results show that applying positive (negative) pressure leads to a decrement (increment) in the DOS at the Fermi level that this calculations suggest a decrement in Tc under application of positive pressure. In the Γ - A path of momentum space, the band which has the dominant role in conduction properties, moves upward when c increases or a decreases, and moves downward when c decreases or a increases. By relaxation of the system under the plane strain, we have studied the behavior of axial lattice parameter c. Our results show that changes in the axial lattice constant c is one third...
P-Doped g-C3N4Nanosheet-Modified BiVO4Hybrid Nanostructure as an Efficient Visible Light-Driven Water Splitting Photoanode
, Article ACS Applied Energy Materials ; Volume 5, Issue 10 , 2022 , Pages 12283-12296 ; 25740962 (ISSN) ; Akhundi, A ; Rahimi, K ; Jaleh, B ; Moshfegh, A. Z ; Sharif University of Technology
American Chemical Society
2022
Abstract
Here, a solution combustion method was employed to construct a photoanode based on bismuth vanadate (BV) composition. To curtail the fast charge recombination, phosphorus-doped g-C3N4 nanosheets (PCNS) in combination with BV are considered a potential approach. The prepared solution combustion facilitated the formation of a BiVO4-PCNS (BV-PCNS) hybrid photoanode with worm-like morphology with a simple setup. The weight ratio of PCNS/BiVO4 and the loading volume/cm2 were optimized to determine the most efficient photoanode. The highest photocurrent density of 0.5 mA/cm2 at 1.23 V vs reversible hydrogen electrode (RHE) under 1 sun illumination was achieved for the hybrid nanostructure at 2 wt...
Structural and Theoretical Study of Some New Rhenium(I) Tricarbonyl Complexes with Non-heterocyclic Diimine Ligands: The Comparison of the σ-Donation and π-accepting Character of the Ligands
, M.Sc. Thesis Sharif University of Technology ; Kia, Reza (Supervisor)
Abstract
Rhenium(I) tricarbonyl complexes with NN-donor ligands display promising properties for potential applications as molecular catalysts for the reduction of carbon dioxide and as biocompatible pro-drugs for the controlled release of carbon monoxide. In this context the diimine type ligands are one of the most widely used bidentate chelating moieties. In this work, several [Re(CO)3(DAB)X] complexes were prepared in a standard manner by replacement of two cis CO groups in the starting bromo- or chloro-pentacarbonylrhenium complexes with 1,4-diazabutadiene (DAB) ligands. Their pseudo-octahedral facial structures were established using FT-IR, 13C-NMR and 1H-NMR and confirmed by X-ray...
Synthesis, Characterization and Photophysical Study of Cationic Cyclometalated Platinum Complexes Containing 2-Phenylpyridine Ligand and its Derivatives
, M.Sc. Thesis Sharif University of Technology ; Jamali, Sirous (Supervisor)
Abstract
The cationic cyclometalated platinum(II) complex [Pt(ⱪ2-2-ppy)(ⱪ1-N-2-ppy)2][OTF], 2, has been prepared by reaction of [PtMe3I]4, 1, with one equiv Ag(OTF) and then three equiv 2-phenylpyridine. The similar complex with formula [Pt(ⱪ2-p′py)(ⱪ1-N-p′py)2][OTF], in which p′py = 2-(3-bromophenyl)pyridine, 4, has been prepared with similar procedure, from the reaction of 1 with one equiv Ag(OTF) and then three equiv of the corresponding cyclometalating ligand. Also, the cationic cyclometalated platinum(IV) complex [Pt(2-(p-tolyl)pyridine)2(Me)(H2O)][OTF], 3, has been prepared from the reaction of 1 with one equiv Ag(OTF) and then three equiv 2-(p-tolyl)pyridine. The structure of complexes 2, 3...
Experimental and theoretical study of the spectroscopic properties and the preparation of 3-benzyl-2H-pyrano[3,2-c]chromene-2,5(6H)-dione
, Article Journal of Molecular Structure ; Vol. 1065-1066, issue. 1 , May , 2014 , pp. 235-240 ; ISSN: 00222860 ; Foroushani, B. K ; Sharif University of Technology
Abstract
Compound 3-benzyl-2H-pyrano[3,2-c]chromene-2,5(6H)-dione(3), was prepared and fully characterized. The vibrational modes (FT-IR) and NMR data ( 1H and 13C chemical shifts) were compared with the results of Density Functional Theory (DFT) method at the B3LYP/cc-PVTZ level. The calculated vibrational frequencies and NMR chemical shifts are in good agreement with the experimental results. The electronic (UV-Vis) spectrum was calculated using the TD-DFT method in CH2Cl2 with the Polarizable Continuum Model using the integral equation formalism variant (IEFPCM) and was correlated to the experimental spectra. The assignment and analysis of the frontier HOMO and LUMO orbitals indicate that...
Structural analysis of Y3Ba5Cu8O 19-δ high-Tc superconductor by ab initio density functional theory
, Article Physica C: Superconductivity and its Applications ; Volume 497 , 15 February , 2014 , 2014, Pages 84-88 ; ISSN: 09214534 ; Rasti, M ; Akhavan, M ; Sharif University of Technology
Abstract
The details of the crystal structure of the recently discovered Y 3Ba5Cu8O18+δ (Y358) superconductor have been determined by ab initio density functional theory. Total energy calculation has been performed for three different suggested structures with different oxygen content. The structure with a center of inversion symmetry and the highest oxygen concentration has the lowest total energy. Thus, it is the best choice for the Y358 crystal structure. By investigating the detailed structure, it is seen that this compound is arranged either of YBa2Cu3O7 and YBaCu2O 5 or YBaCu2O5 and BaCuO2 substructural blocks in the c direction. The difference between the total energy of Y358 compound and the...
Efficient photo-dissociation of CH4 and H2CO molecules with optimized ultra-short laser pulses
, Article AIP Advances ; Volume 5, Issue 11 , 2015 ; 21583226 (ISSN) ; Irani, E ; Sadighi Bonabi, R ; Sharif University of Technology
American Institute of Physics Inc
2015
Abstract
The fragmentation dynamics of CH4 and H2CO molecules have been studied with ultra-short pulses at laser intensityof up to 1015Wcm-2. Three dimensional molecular dynamics calculations for finding the optimized laser pulses are presented based on time-dependent density functional theory and quantum optimal control theory. A comparison of the results for orientation dependence in the ionization process shows that the electron distribution for CH4 is more isotropic than H2CO molecule. Total conversion yields of up to 70% at an orientation angle of 30o for CH4 and 65% at 900 for H2CO are achieved which lead to enhancement of dissociation probability
Optical absorption and electronic spectra of chlorophylls a and b
, Article RSC Advances ; Volume 6, Issue 111 , 2016 , Pages 109778-109785 ; 20462069 (ISSN) ; Irani, E ; Mazarei, M ; Rasti, S ; Azar, Y. T ; Rezakhani, A. T ; Mashaghi, A ; Shayeganfar, F ; Anvari, M ; Heydari, T ; Tabar, A. R ; Nafari, N ; Vesaghi, M. A ; Asgari, R ; Rahimi Tabar, M. R ; Sharif University of Technology
Royal Society of Chemistry
2016
Abstract
Photosynthesis includes capturing sunlight by an assembly of molecules, called chlorophylls, and directing the harvested energy in the form of electronic excitations to the reaction center. Here we report, using real-space density functional theory and time-dependent density functional theory together with GW calculations, the optical and electronic properties of the two main chlorophylls in green plants, namely, chlorophylls a and b. Furthermore, we estimate the dipole and primitive quadrupole electric moments of these molecules. We employ Casida's assignment ansatz to study the absorption spectra of the chlorophylls in the two main red and blue regions at various environments with...
The control of electron quantum trajectories on the high-order harmonic generation of CO and N2 molecules in the presence of a low frequency field
, Article Journal of Chemical Physics ; Volume 148, Issue 14 , 2018 ; 00219606 (ISSN) ; Sadighi Bonabi, R ; Mohsen Nia, M ; Irani, E ; Sharif University of Technology
American Institute of Physics Inc
2018
Abstract
In the present work, an efficient method is theoretically investigated for extending high-order harmonics and ultrashort attosecond pulse generation in N2 and CO molecules by using the time-dependent density functional theory approach. Our results show that by utilizing chirped laser field in the presence of a low frequency field, not only is the harmonic cutoff extended remarkably but also the single short quantum trajectory is selected to contribute to the harmonic spectra. When a low frequency field is added to the two-color chirped laser field, the long quantum trajectories are suppressed and only the short quantum trajectories contribute to the higher harmonic emission mechanism. As a...
Influence of remote intramolecular hydrogen bonding on the acidity of hydroxy-1,4-benzoquinonederivatives: A DFT study
, Article Journal of Physical Organic Chemistry ; Volume 32, Issue 4 , 2019 ; 08943230 (ISSN) ; Fattahi, A ; Sharif University of Technology
John Wiley and Sons Ltd
2019
Abstract
In this study, the effects of the remote intramolecular hydrogen bonding on the acidity of hydroxy-1,4-benzoquinone derivatives have been investigated ab initio by employing density functional theory (DFT) methods. The computational studies were performed for both gas and solution (H 2 O, DMSO, and MeCN solutions) phases. Our results indicated that remote hydrogen bonding could play an important role in increasing the acidity of hydroxy-1,4-benzoquinone. Noncovalent interaction reduced density gradient (NCI-RDG) methods were used to visualize the attractive and repulsive interactions in the studied acids and their conjugate bases. Natural bond orbital (NBO) analysis was performed to confirm...
Computational study of spin caloritronics in a pristine and defective antimonene nanoribbon
, Article Physica E: Low-Dimensional Systems and Nanostructures ; Volume 120 , 2020 ; Faez, R ; Darvish, G ; Sharif University of Technology
Elsevier B.V
2020
Abstract
In this paper, by using first-principle density functional theory (DFT) combined with non-equilibrium Green's function (NEGF), thermally induced spin current in zigzag and armchair Antimonene Nanoribbon (SbNR) is investigated. Also, we obtain higher spin current in Armchair nanoribbon (ANR) than zigzag nanoribbon (ZNR), because the start energy of transmission for ANR is closer to the Fermi level than ZNR. The results show that the device has a perfect spin Seebeck effect under temperature difference without gate voltage or bias voltage. For the ANR configuration, the competition between spin up holes and spin down electrons leads to negative differential behavior of charge current, which is...
Two-dimensional porous graphitic carbon nitride C6N7 monolayer: first-principles calculations
, Article Applied Physics Letters ; Volume 119, Issue 14 , 2021 ; 00036951 (ISSN) ; Faraji, M ; Fadlallah, M. M ; Abdolhosseini Sarsari, I ; Jappor, H. R ; Fazeli, S ; Ghergherehchi, M ; Sharif University of Technology
American Institute of Physics Inc
2021
Abstract
The fabrication of the C6N7 monolayer [Zhao et al., Sci. Bull. 66, 1764 (2021)] motivated us to discover the optical, structural, mechanical, and electronic properties of the C6N7 monolayer by employing the density functional theory (DFT) method. We find that the shear modulus and Young's modulus of the C6N7 monolayer are smaller than the relevant values of graphene. However, Poisson's ratio is more significant than that of graphene. Applying the PBE (HSE06) functional bandgap of the C6N7 monolayer is 1.2 (1.97) eV, and the electronic dispersion is almost isotropic around the Γ point. C6N7 is more active in the ultraviolet region as compared to the visible light region. This study provides...
Effect of the pyrrolic nitrogen functional group in the selective adsorption of CO2: GCMC, MD, and DFT studies
, Article Energy and Fuels ; Volume 35, Issue 19 , 2021 , Pages 15918-15934 ; 08870624 (ISSN) ; Mirzaee Valadi, F.M ; Latifi Pour, M ; Rashtchian, D ; Gholami, M. R ; Sharif University of Technology
American Chemical Society
2021
Abstract
In this paper, the pyrrolic nitrogen functional group's presence is investigated in the selective adsorption of CO2. The grand canonical Monte Carlo (GCMC), molecular dynamics (MD), and density functional theory (DFT) were used for this study's goal. GCMC was used to calculate adsorption isotherms, selectivity, and isosteric heats. MD was used to calculate the radial distribution function (RDF) and diffusion. Reactivity parameters, electrostatic potential (ESP), reduced density gradient (RDG), and independent gradient model (IGM) were calculated using DFT. Adsorption isotherms, selectivity, and isosteric heats demonstrated that the NH group caused the selective adsorption of CO2 among CH4,...
Introducing an effective method for extending the high harmonic spectrum plateau from gas targets
, Article Journal of Physics B: Atomic, Molecular and Optical Physics ; Volume 54, Issue 4 , February , 2021 ; 09534075 (ISSN) ; Monfared, M ; Majles Ara, M. H ; Sadighi Bonabi, R ; Sharif University of Technology
IOP Publishing Ltd
2021
Abstract
An effective semi-classical method is introduced for controlling the high-order harmonic generation process and extending the cutoff frequency. This method is capable of defining the proper specification of the driving laser for maximizing the cutoff frequency. This method is evaluated by examining the high harmonic spectrum from the hydrogen atom and the fluorine (F2) molecule irradiated by single-, two-, and three-color laser fields. This study is done using the time-dependent density functional theory in a three-dimensional space. The results show that the single-, two-, and three-color laser pulses tuned by proper specifications could extend the cutoff frequency by up to 85%, 176%, and...
Effects of ligands on (de-)enhancement of plasmonic excitations of silver, gold and bimetallic nanoclusters: TD-DFT+TB calculations
, Article Physical Chemistry Chemical Physics ; Volume 23, Issue 33 , 2021 , Pages 17929-17938 ; 14639076 (ISSN) ; Pototschnig, J ; Jamshidi, Z ; Visscher, L ; Sharif University of Technology
Royal Society of Chemistry
2021
Abstract
Metal nanoclusters can be synthesized in various sizes and shapes and are typically protected with ligands to stabilize them. These ligands can also be used to tune the plasmonic properties of the clusters as the absorption spectrum of a protected cluster can be significantly altered compared to the bare cluster. In this paper, we computationally investigate the influence of thiolate ligands on the plasmonic intensity for silver, gold and alloy clusters. Using time-dependent density functional theory with tight-binding approximations, TD-DFT+TB, we show that this level of theory can reproduce the broad experimental spectra of Au144(SR)60 and Ag53Au91(SR)60 (R = CH3) compounds with...
Deep oxidative desulfurization via rGO-immobilized tin oxide nanocatalyst: Experimental and theoretical perspectives
, Article Advanced Powder Technology ; Volume 33, Issue 3 , 2022 ; 09218831 (ISSN) ; Kazemeini, M ; Hasannia, S ; Ekramipooya, A ; Sharif University of Technology
Elsevier B.V
2022
Abstract
In this contribution, reduced grapheme oxides (rGO) with immobilized tin oxide (SnO2) nanocatalysts were synthesized via the Incipient Wetness Impregnation (IWI) method. To characterize the SnO2/rGO composites, several analyses including the; XRD, Raman, FTIR, ICP-OES, BET-BJH, XPS, TEM, and TPD were utilized. Then the effects of parameters including reaction time, total metal loading, and the initial sulfur concentration of model fuel in the dibenzothiophene (DBT) oxidation desulfurization process were evaluated. After determining the optimal conditions for the aforementioned parameters, the influences of 3 effective factors of the molar ratio of oxidant/substrate (O/S), the molar ratio of...
Thermochemical Properties of Thymine & Deoxythymidine
, M.Sc. Thesis Sharif University of Technology ; Fattahi, Alireza (Supervisor)
Abstract
Nowadays, there is no doubt about the importance of investigation of physicochemical properties of nucleosides in order to determine the structure of these biopolymers. Nucleotides have a variety of roles in cellular metabolism. They are the constituents of nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), the molecular repositories of genetic information. The metal ions play a significant role in several biological processes. Synthesis, replication, and cleavage of DNA and RNA as well as their structure integrity are affected by the presence of these ionized metals in the cell nucleus. To understand the role of cations in the biophysics of DNA, it is necessary first to...