Sharif Digital Repository

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... 

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... 

In this study, orthosilicate materials with chemical formula of Li2MSiO4 (M one or two transition metal/metals) were investigated experimentally and theoretically as cathode material of Li-ion batteries. The most important material in this category i.e. Li2FeSiO4 was synthesized by three methods including nitrate-based sol-gel, oxalate-based solid state reaction and oxide-based solid state reaction. Based on XRD and SEM evaluations, grain size of synthesized powders was estimated to be between 15 to 100 nanometers. Of these three methods, oxide-based solid state reaction was employed in this study for the first time. This syntheses method is very important due to the significant lower... 

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... 

The purpose of this research is to introduce a heterostructure for Vertical Tunneling Field-Effect Transitors, calculating its band structure and finding the tight binding hopping parameters of its structure. To do this, we must first study different kinds of heterostructures and choose the most suitable one among them. In this research, we selected the three-layer graphene eSoM2-BN-Gr_h for its high on/off current ratio (〖10〗^6). To find the band structure, first we should construct unit cell and then find its crystal structure after relaxation. The lattice constant for graphene and is the same, but the lattice constant of graphene andeSoM2-BN-Gr_h is different . The number of atoms in the... 

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... 

This thesis deals with a theoretical and experimental investigation of different approaches for reduction of electronic recombination in the semiconductor/Dye interface of dye sensitized solar cells (DSSC) including dye coverage, core-shell structures and energy level distributions. Interface of ZnO/TiO2 in the core-shell structure have been studied by density functional theory and the energy level distribution of surface atoms, recombination and Fermi level changes, open circuit voltage and surface dipole distributions have been discussed.
The presence of TiO2 shell increases the ZnO surface dipole moment, and shifts the ZnO conduction and valence bands to higher energies. Also, it... 

The advent and advancement of technology through the conversion of Gas-Synthesis (a mixture of CO and H) into liquid hydrocarbons, by Fischer- Tropsch synthesis (FTS) gives more promising future in this field. Metals such as cobalt, nickel, zinc and iron are used as catalysts for FTS. Studies have shown that the surface structure of metal catalyst has a great influence on the process, and leads to different products and transition states. Iron has been known the most used and the most cost-effective metal catalyst in FTS. Different surfaces of Iron have different catalytic roles. In our work, Fe(100) -that is the most stable after Fe(110) and is known as the most active iron’s surface in... 

There is no satisfactory agreement between theory and experiment in the Hartree-Fock (HF) and density functional theory (DFT) calculation for metals, semiconductors and metals. It is clear that this discrepancy is attributed to the neglecting of correlation. For example, experimentally
LiF have the largest band gap about 13.6 eV among the alkali halides and show an exciton peak at 12.6 eV . Brener have obtained a value of 22.9 eV for LiF band gap in the HF approximation. DFT has been very successful tool in calculating the ground-state properties of materials. As
we expect, the band gap in LiF are underestimated in the local density approximation (LDA) calculation (about 8.3 eV) .... 

Sulfur dioxide is known as an acidic gas and one of the standard pollutants in determining air quality. This gas mostly enters into the atmosphere by flue gas causing many environmental problems. In order to remove this gas, various methods are used. One of the suitable methods to reduce the emission of this pollutant in low concentrations is the use of Metal-Organic Frameworks (MOF) as an adsorbent. One of these Metal-Organic Frameworks is NH2-MIL-53(Al) that owing to its relatively good stability under wet and acidic conditions, has been chosen to adsorb sulfur dioxide in this research. In most studies on SO2 adsorption, often MOFs with a long synthesis time, high synthesis cost, and/or... 

This work investigates adsorption and possible dissociation of a number of small molecules on small clusters and carbonic surface. Theoretical study of carbon monoxide adsorption on SixGe4_x(x=0–4) nano-clusters has been carried out using MPW1B95 density functional. The geometry, adsorption energy, charge distribution, and vibrational frequency of CO adsorption on all possible structures were investigated. The maximum vibrational frequency changes occur in the bridge structures while the most stable structures occur when CO adsorbs on one silicon atom in a flat surface. Adsorption energies of CO on one Si atom are by far more negative than the corresponding value for on Ge atom. Theoretical... 

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... 

The bis-cyclometalated platinum(II) complexes [Pt(ptpy)2], 3, and [Pt(fppy)2], 4, in which, ptpy = 2-(p-tolyl)pyridine and fppy = 2-(2,4-difluorophenyl)pyridine have been prepared. The reaction of 3 with one equiv [Au(PPh3)]+ (prepared from the reaction between AuCl(PPh3) and AgOTf) gave the heterobinuclear complex [Pt(ptpy)2Au(PPh3)].OTf, 5, by formation of a Pt→Au dative bond. The structure of all complexes were characterized using multinuclear NMR spectroscopy in solution phase and the structures of 4 and 5 determined using X-ray crystallography in solid state. The structure of heterobinuclear complex 5 shows an unusual Pt-Au bond that supported by Au-Cipso bond. The absorption and... 

With the development of urbanization, industrialization, explosive population growth, and environmental degradation, the world is facing a serious challenge of water pollution. Nowadays, the water-soluble pollutant such as heavy metals and dyes brought a serious threat to the aquatic organisms and human health due to their non-degradability and carcinogenicity.With the purpose of future security and to restore ecological balance, it is essential to give much significance towards the removal of unwanted toxic contaminants from water resources. In this regard, the removal of toxic pollutants from wastewater using Metal-organic frameworks (MOFs) -based composites is considered as one of the... 

To account for certain essential features of material such as micro-structure effects and dispersive behaviour and optical branches in dispersion curves, a fundamental departure from classical elasticity to generalized continuum theories is required. Among the generalized continuum mechanics, micromorphic elasticity is capable of capturing these physical phenomena completely. In the mathematical framework of micromorphic elasticity, in addition to the traditional elastic moduli tensors, some additional tensors are introduced in the pertinent governing equations of motion. A precise evaluation of the numerical values of the aforementioned elastic moduli tensors in the realm of the... 

Acidity values of some compound (e.g., alkanes, alcohols, carboxylic acids and amines) with or without boron substitute have been studied theoretically to evaluate the influence of boron on acidity of organic functional groups. We have derived the unoccupied reactive orbital that show the maximum localization on the boron pπ atomic orbital overlapping with the lone-pair orbital of an electron donor. Localization of unoccupied reactive orbital on the boron pπ atomic and the polarizability of the boron center are two factors which affect acidity values of functional groups. Conformational searching was performed using MM (Molecular Mechanics). The most important conformations were optimized at... 

Nowadays, the population growth and industrial development have caused pollution of air, water, and soil, which this turned into in a global challenge. Thus, replacing the running-out fossil fuels with renewable sources of energy is an important issue facing research and scientific communities. One of the methods to generate clean energy is hydrogen production through water splitting reaction inside photoelectrochemical cells using an appropriate semiconductor. Upon the light illumination, rates of charge transfer and recombination in semiconductors heterostructure (as photoanodes) are determining factors for efficiency of these cells. If electron transfer occurs faster (in a shorter time... 

The X-ray attosecond pulses have many useful applications for studying atomic and sub-atomic scales phenomena in attosecond scale duration. Generation and optimization of high-order harmonics is an efficient way to produce such attosecond pulses which are studied in this thesis. There are several limitations in the attosecond pulse generation such as low efficiency of high-order harmonics, long duration of output pulses and the impossibility of producing an attosecond pulse with any desired wavelength in the x-ray region. Therefore, more investigations into high harmonic generation and fully control and optimization of this process is significant. In this thesis, high harmonic generation... 

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... 

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...