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density-functional-theory
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Experimental Study of Oxygen Reduction Reaction (ORR) on Cu-alloys, Electrocatalysts in Alkaline Solution and Theoretical Investigation of Oxygen Adsorption on Cu-alloys Nano-clusters
, Ph.D. Dissertation Sharif University of Technology ; Gobal, Fereydoon (Supervisor)
Abstract
In this study, electrochemical oxygen reduction reaction (ORR) was studied on Cu, Pd, Rh, Pd-Cu and Rh-Cu alloys in alkaline solution. Pd-Cu and Rh-Cu alloys were prepared by electrochemical methods. On copper electrode it is found that direct oxygen reduction is accompanied by the electrochemical reductions of copper oxides. Also, mechanism and kinetics of reaction change as the amount of copper oxides increase on the surface. For electrodeposited alloys, it is indicated that the reactivity of Pd-Cu and Rh-Cu alloys toward oxygen reduction is higher than pure Pd and pure Rh. The maximum reactivity among Pd-Cu alloys is related to the sample with 24.5% copper content while the maximum...
Exploring of Hydrogen Bond Effect on Acidity Value for Multifunctional Alcohols in Gas Phase & Nonaqueous Solvent via DFT Method
, M.Sc. Thesis Sharif University of Technology ; Fattahi, Alireza (Supervisor)
Abstract
Hydrogen bond is a type of molecular bonds which occurs between hydrogen and a highly electronegative atom( usually F, N and O) and results to special properties. Polyols and multihydroxyl compounds are among substances which have special properties such as acidity due to the existence of hydrogen bond in their molecular structure. Acidity in these compounds is a result of having stable anions due to intramolecular hydrogen bands. The existence of an electronegative group in addition to hydroxyl groups leads to increase the acidity in these substances. In this project acidities of some polyols and multihydroxyl compounds were calculated in both gas phase and solution phase( DMSO,...
Investigation of Mechanical Properties of Graphene
, Ph.D. Dissertation Sharif University of Technology ; Iraji Zad, Azam (Supervisor) ; Rafii-tabar, Hashem (Supervisor)
Abstract
The unique properties of graphene due to the presence of massless Dirac fermions, high surface to volume ratio, high crystal quality in 2D, and high mechanical strength, recommend it as a promising material for technologies such as nanoelectromechanical systems (NEMS) and nanosensors. Use of graphene in nanodevices is accompanied by induced strains and stresses. Therefore it is important to study the mechanical properties of graphene. In present thesis, we synthesized graphene using both mechanical cleavage of graphite and chemical method. In the chemical method graphene oxide is prepared by oxidation and exfoliation of graphite. The graphene oxide sheets were reduced to prepare graphene...
Silicon Vacancy in 4H-SiC: Many-body Electronic Structure
, M.Sc. Thesis Sharif University of Technology ; Vesaghi, Mohammad Ali (Supervisor)
Abstract
The silicon vacancy in silicon carbide is a strong emergent candidate for applications in quantum information processing. 4H, 6H and 3C polytypes of SiC all host coherent and optically addressable defect spin states. Electron paramagnetic resonance (EPR) and optically detected magnetic resonance (ODMR) investigations suggest that silicon vacancy point defects in SiC possess properties similar to those of the NV center in diamond. We provide a new theoretical frame to explain a wider range of experimental results. Employing a proposed generalized Hubbard model, with the help of electronic structure programs, DFT, second quantization, and various computational approaches, we obtain new...
Theoretical Investigation of Hydrogen Bonding Effects on Acidity Enhancement of Beta Diketones in Gas and Solution Phase
, M.Sc. Thesis Sharif University of Technology ; Fattahi, Alireza (Supervisor) ; Mahmoodi Hashemi, Mohammad (Supervisor)
Abstract
Hydrogen bonding is an important weak interaction encountered in gas and liquid, as well as solid phase. The hydrogen bond plays a very vital role in many life processes and is one of the most frequently used terms in chemistry and biology. Beta diketones have several applications in organic, inorganic and analytical chemistry. Different substituents can affect the acidity of beta diketones. Investigation have shown that hydroxyl function group can increase the acidity of many organic molecules through interamolecular hydrogen bonding. The goal of this project is to investigate the acidity of hydroxyl containing beta diketones in the gas and solution phase. All the gas phase optimizations...
Theoretical Study of Organic Pollutants Adsorption on Graphene, Doped Graphene and Defective Graphene Nanosheets
, M.Sc. Thesis Sharif University of Technology ; Rahman Setayesh, Shahrbanou (Supervisor)
Abstract
Among the xenobiotic compounds, chlorophenols are considered to be as the most dangerous compounds for the environment and living organisms. These compounds are abundantly found in the wastewater of many chemical industry factories. In this research, by using Gaussian software and density functional theory at the level of B3LYP / 6-31G (d, p),the adsorption of molecules such as phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol over graphene, nitrogen and boron doped graphene sheet are studied. The most stable configurations were determined and adsorption energies were calculated. In addition, to understand the adsorption mechanism, electron properties such as state density and...
Theoretical Investigation of Basicity and Proton Transfer Energy of Protic Energetic Ionic Liquids in the Gas Phase and in Solution
, M.Sc. Thesis Sharif University of Technology ; Rahman Setayesh, Shahrbanoo (Supervisor)
Abstract
The use of energetic ionic liquids as hypergolic fuels, has low toxicity and environmental risk relative the hypergolic fuels such as the hydrazine. In this research by using Gauss view and Gaussian softwares and density functional theory and MP2 methods at the level of B3LYP/6-311G(d,p), the proton transfer from the cations to anions for a set of hypergolic ionic liquids in the gas and solution phases were studied. The most stable configuration of cations and anions are determined. The interaction energies of the selected cations and anions, proton affinities and basicity properties of these hypergolic anions are calculated. The result represents that the lower proton affinity and basicity...
Investigation of Nano-particle Structures CdS using Density Functional Theory
, M.Sc. Thesis Sharif University of Technology ; Nafari, Naser (Supervisor) ; Rahimitabar, Mohammad Reza (Supervisor)
Abstract
In this project, we have studied the geometric and electronic structures of CdS nano-particles. The bulk CdS is known to be a semiconductor with the experimental energy gap of 2.42eV which is more than twice the theoretical resuls based on LDA or GGA energy functionals used in the density functional theory. However the calculations based on Kohn-Sham formalism used in DFT (KS-DFT) predicts the geometric structure of bulk semiconductors fairly well. Therefore, we have employed the KS-DFT formalism for our CdS nano-particles and have used the Gaussian as well as SIESTA computer codes to predict the geometric structures of these nano-semiconductor-particles. For calculating their electronic...
Electronic Structure and Phonon Calculations for Unconventionaly358, Lbco and 1111-Iron Pnictide Superconductors
, Ph.D. Dissertation Sharif University of Technology ; Akhavan, Mohammad (Supervisor)
Abstract
Experiments indicate the important role of the electron-phonon interaction and crystal lattice effects on the electronic and superconductivity properties of the unconventional superconductors. Thus, in the theoretical studies of the mechanism of unconventional superconductivity, role of phonons and crystal lattice distortions can not be ignored. Based on this fact, in this dissertation, it has been tried to investigate the effect of phonons and lattice distortions in the electronic properties of some unconventional superconductors. For this purpose, we have used the ab-initio, density functional theory of the ground state and perturbed states, which is the most suitable approach when it is...
Effect of Co Doping on Crystal and Electronic Structure of BaFe2-xCoxAs2
, M.Sc. Thesis Sharif University of Technology ; Khosroabadi, Hossein (Supervisor) ; Akhavan, Mohammad (Supervisor)
Abstract
The discovery of the iron-based superconductors attracted much experimental and theoretical attention in the recent years. BaFe2As2 is one of the highlighted materials which is the antiferromagnetic metal (below Neel temperature) and undergoes to superconducting and non-magnetic state by variety of doping, usually accompanied by a structural phase transition. Superconductivity is appeared in this system by doping Co and Ni at the Fe sites which is one of the excited situations in the physics of superconductors, where the magnetic doping suppresses the superconducting state. So, the study of Co doping of the electronic structure of this system, might lead us to better understanding of the...
Shaping of Laser Pulse for Molecular Dissociation
, M.Sc. Thesis Sharif University of Technology ; Saddighi Bonabi, Rasoul (Supervisor)
Abstract
In this project, ionization and dissociation of nitrogen, methane and formaldehyde molecules through interaction by intense femto-second lasers have been investigated. The optimum shape of laser pulses for dissociation of methane and formaldehyde molecules for controlling the dissociation paths into desired products are obtained. Based on time dependent density functional theory and quantum optimal control theory, the calculations are carried out in intensities at the range of 1014-1016 Wcm-2 with pulse durations of 4 -20fs. Octopus package is used as a powerful computational program. By using, quantum optimal control theory, optimum laser pulses with manipulation of amplitude, phase and...
Effect of Impurity and Starin on Quantum Conductance of Semiconductor Carbon Nanotube Nanotubes and Resistance of Contact Between Metal and Nanotube
, M.Sc. Thesis Sharif University of Technology ; Faez, Rahim (Supervisor) ; Sarvari, Reza (Supervisor)
Abstract
In this paper effect of Nitrogen and Boron doping on the quantum conductance of semiconductor carbon nanotubes is investigated. Calculations are performed using density function theory in conjunction with Green function techniques and the quantum conductance is calculated. Transmission and conductance of the electronic devices in nanometer scale depend on band structure and density of states. Our results show that quantum conductance of semiconductor carbon nanotube is increased by replacing Nitrogen and Boron in its structure. The value of increasing conductance depends on the type of impurity. It is greater for Nitrogen doping in comparison with Boron. Effect of strain on the quantum...
DFT Study on Mechanism and Kinetic of Thiotepa and Tepa Interaction with its DNA Receptor
,
M.Sc. Thesis
Sharif University of Technology
;
Fattahi, Alireza
(Supervisor)
Abstract
N, N′, N″-triethylenethiophosphoramide (Thiotepa) and its oxo analogue (Tepa) as the major metabolite are trifunctional alkylating agents with a broad spectrum of antitumor activity. In vivo and vitro studies show alkylation of DNA by Thiotepa and Tepa can follow two pathways, but it remains unclear which pathway represents the precise mechanism of action. In pathway 1, these agents are capable of forming cross-links with DNA molecules which can be carried out via two different mechanisms. In the first mechanism, the ring opening reaction is initiated by protonating the aziridine, which then becomes the primary target of nucleophilic attack by the N7-Guanine of DNA. The second one is the...
Supplementary Effects of Fluorine Doping and Pressure on Electronic Structure of LaO1-xFxFeAs Superconductor
, M.Sc. Thesis Sharif University of Technology ; Khosroabadi, Hossein (Supervisor) ; Akhavan Farshchi, Mohammad (Co-Advisor)
Abstract
Iron based superconductors that are studied more in recent years, have the same and different features with copper oxide high temperature superconductors which they can help in solving problems related to high temperature superconductors. In addition, these compounds have attractive physical characteristics such as superconductivity despite of presence of magnetic Iron element or other magnetic elements like nickel and cobalt (In other superconductivity groups, low doping of magnetic elements destroys superconductivity) and also concurrent presence of magnetic and superconductivity phases. The most reported transition temperature in these compounds is 56.3K in Gd0.8Th 0.2FeAsO compound....
Conformational Study of Lidocaine and Bupivacaine by Quantum Mechanical Methods
, M.Sc. Thesis Sharif University of Technology ; Tafazoli, Mohsen (Supervisor)
Abstract
In this thesis the structure and potential energy surfaces of Lidocaine and bupivacaine were studied by DFT method at B3LYD level calculation using 6-311++G basis set. Both compounds were calculated in water, dimetylsulfoxide, and carbontetracholoride as the solvent using the PCM model.Since the molecules meant to be studied were polar, level of energy in polar solvent is higher than non-polar solvent . The most considerable increase was observed in the amount of energy at 0.01 hartree for water compared with carbon tetracholoride. By changeing in solvent environment the most considerable difference in bond length was observed as 0.01 Ǻ.The spin spin coupling constants 1JCH, 2JCH, 2JHH,...
Study of Conformational of Fentanyl by Quantum Mechanic Methods
, M.Sc. Thesis Sharif University of Technology ; Tafazzoli, Mohsen (Supervisor)
Abstract
The study of energy and structure of fentanyl was performed by using quantum mechanical calculations method of Density Functional Theory(DFT) at the computational level B3 L YP and the basis set 6-311++G^(**). Proton-proton and proton-carbon coupling constants were computed around dihedral angles and . All Karplas equation indicating the relation between coupling constants (namely 〖(_^"1" )"J" 〗_"CH" ^ ، 〖(_^"2" )"J" 〗_"HH" ^ ، 〖(_^"2" )"J" 〗_"CH" ^ ، 〖(_^"2" )"J" 〗_"CH" ^ ، 〖(_^"3" )"J" 〗_"CH" ^ ، 〖(_^"3" )"J" 〗_"HH" ^ and appropriate dihedral angles were extracted. The impact of three water solvents, dimethyl sulfoxide, and carbon tetrachloride with different polarity on the values of...
Synthesis, Characterization, and Enhanced Optical/Electronic Properties of g-C3N4 Nanosheets for Water Remediation
, Ph.D. Dissertation Sharif University of Technology ; Moshfegh, Alireza (Supervisor) ; Asgari, Reza (Supervisor) ; Naseri, Naimeh (Co-Supervisor)
Abstract
A global concern has arisen owing to rapid industrial development and population growth, resulting in energy scarcity and earth pollution. In this regard, developing green and sustainable methods for producing clean energy and solving environmental pollution problems have absorbed enormous attention. Among various auspicious strategies, semiconductor photocatalysis has been widely studied in recent years owing to its capabilities to obtain hydrogen as an energy carrier, to remove organic pollutants, and to reduce CO2 emission by converting solar energy into chemical energy. Recently, a metal-free semiconductor photocatalyst based on graphitic carbon nitride, g-C3N4, has received much...
Reduction of Sulfur Content of Model Feed by Oxidative Process in them Presence of Carbon Structures Based W-Mo Nanocatalysts
, Ph.D. Dissertation Sharif University of Technology ; Kazemini, Mohammad (Supervisor) ; Rashidi, Alimorad (Supervisor) ; Hajjar, Zeinab (Co-Supervisor)
Abstract
In this research, molybdenum and tungsten catalysts modified with cobalt and nickel on a carbon support have been synthesized and investigated in the oxidation desulfurization process. A model fuel was used to evaluate the synthesized catalysts. This model fuel was n-decane. dibenzothiophene was also used as a sulfur model. The synthesized catalysts were subjected to various analyzes such as XRD, FTIR, Raman, BET-BJH, NH3-TPD, TEM and ICP-OES for structural evaluation. On the other hand, synthetic parameters such as metal loading rate, molar or weight ratio of secondary metal (cobalt and nickel) to primary metal (molybdenum and tungsten) and molar ratio of citric acid to primary metal as...
Density Functional Theory Study of Electric Fields Effect on Gold Nanoparticles
, M.Sc. Thesis Sharif University of Technology ; Khoei, Amir Reza (Supervisor) ; Shahsavari,Rozbeh (Supervisor)
Abstract
Unique properties of Gold at nanoscale have made it one of the most popular substances used in nanotechnology. The interaction of Gold and Thiolates is one of the most favorite fields of research. Extensive studies about this interaction have revealed the importance and usage of this system in future technology. Due to difficulties of experimentationat nanoscale, computer simulations arevery important. Although interatomic potentials lead to higher computational speeds, they have deficiencies in precise simulation of some phenomena. Ab-initio methods, such as density functional theory, provide powerful tools to increase the accuracy. In this research, the interaction of gold and thiolates...
Investigation of intense femto-second laser ionization and dissociation of methane with time-dependent density-functional approach
, Article Chemical Physics Letters ; Vol. 604 , 2014 , Pages 60-67 ; ISSN: 00092614 ; Sadighi Bonabi, R ; Anvari, A ; Sharif University of Technology
Abstract
Three dimensional calculations of electronic dynamics of CH4 in a strong laser field are presented with time-dependent density-functional theory. Time evolution of dipole moment and electron localization function is presented. The dependence of dissociation rate on the laser characters is shown and optimal effective parameters are evaluated. The optimum field leads to 76% dissociation probability for Gaussian envelope and 40 fs (FWHM) at 10 16 W cm-2. The dissociation probability is calculated by optimum convolution of dual short pulses. By combining of field assisted dissociation process and Ehrenfest molecular dynamics, time variation of bond length, velocity and orientation effect are...