Sharif Digital Repository

A series of thiophene-based donor-acceptor-donor (D-A-D) oligomer substituted metalloporphyrins (MPors) with different 3d central metal-ions (M = Co, Ni, Cu, and Zn) were systematically investigated to screen efficient hybrid photocatalysts for CO2 reduction based on density functional theory (DFT) and time-dependent DFT simulations. Compared with base MPors, the newly designed hybrid photocatalysts have a lower bandgap energy, stronger and broader absorption spectra, and enhanced intermolecular charge transfer, exciton lifetime, and light-harvesting efficiency. Then, the introduction of D-A-D electron donor (ED) groups into the meso-positions of MPors is a promising method for the... 

Although the simple assembly line balancing problem (SALBP) is the topic of many studies, typically they either consider minimizing the number of stations for a given cycle time (called type one), or minimizing the cycle time for a given number of stations (called type two). Rarely, type E of the problem has been considered. In the type E, cycle time and number of stations are both decision variables, and the objective is to maximize the line efficiency. This paper presents a mixed integer linear programming formulation for the type E simple assembly line balancing problem. Moreover, to further strengthen the presented formulation, two enhancement techniques in the form of valid inequalities... 

Transition metal lithium orthosilicates are of interest as cathode materials for lithium batteries. Density functional theory (DFT) calculations were performed to evaluate the structural and electrochemical properties of the different polymorphs of Li2MnSiO4. Our computational studies predict superior properties for the Pmn21 polymorph even after extraction of two Li per formula unit. We state that the shortcomings observed for Li2MnSiO4 as a cathode are caused by two mechanisms. Switching of the magnetic state occurs during the first cycles. The subsequent transition, under delithiated conditions, from the Pmn21 or Pmnb polymorphs to the electrochemically weakest P21/n polymorph is the... 

We report the structural, spectroscopic, and computational studies of two new Re(i) tricarbonyl complexes bearing 2,3,6,7-tetraphenyl-1,4,5,8-tetraazaphenanthrene (Ph4TAP) and 4,5-diazafluoren-9-one (dafone) having a coordinated perrhenate group obtained via in situ superoxidation of Re(i) to Re(vii); intramolecular and intermolecular n → π∗ interactions are dominant and stabilize the molecular geometry and crystal packing. This journal is © The Royal Society of Chemistry  

Herein, we report the synthesis, characterization and combined structural and full computational analysis of noncovalent interactions in a new hydrazine ligand and its two chlorido- and endo-nitrito-rhenium(I) tricarbonyl complexes. The analysis of crystal structures has been accompanied by comprehensive computational studies of the noncovalent interactions utilizing the quantum theory of atoms in molecules (QTAIM), natural bond orbitals (NBO), independent gradient model (IGM), and electron localization function (ELF) to shed light on the nature of the interactions. On the other hand, comprehensive energy decomposition analysis (EDA) by extended transition state coupled with natural orbitals... 

Investigation of the X-ray structure of the newly prepared [Ru(NO)(2,6isopPh2Aceq)Cl3] (2,6isopPh2Aceq = bis(2,6-diisopropylphenylimino)acenaphthenequinone) complex revealed for the first time the π-hole interaction involving the coordinated nitrosyl group with DMSO as the solvent of crystallization in the crystal lattice. Processing of CSD data showed only one reported structure. A significant feature of the structure is the presence of n → π∗, π → σ∗, and n → σ∗ interactions due to the coordinated nitrosyl and chloro groups and DMSO. © 2020 The Royal Society of Chemistry  

We present a computational study on the electrical behavior of the field-effect transistor based on vertical graphene-hBN- χ 3 borophene heterostructure and vertical graphene nanoribbon-hBN- χ 3 borophene nanoribbon heterostructure. We use nonequilibrium the Green function formalism along with an atomistic tight-binding (TB) model. The TB parameters are calculated by fitting tight-binding band structure and first-principle results. Also, electrical characteristics of the device, such as ION/IOFF ratio, subthreshold swing, and intrinsic gate-delay time, are investigated. We show that the increase of the hBN layer number decreases subthreshold swing and degrades the intrinsic gate-delay time.... 

In this paper, for the first time, we present a computational study on the electrical behavior of the field-effect tunneling transistor based on vertical graphene-MoS2 heterostructure and vertical graphene nanoribbon-MoS2 heterostructure. Our simulation is based on nonequilibrium Green's function formalism along with an atomistic tight-binding (TB) model. The TB parameters are obtained by fitting the bandstructure to first-principle results. By using this model, electrical characteristics of device, such as I ON/I OFF ratio, subthreshold swing, and intrinsic gate-delay time, are investigated. We show that the combination of tunneling and thermionic transport allows modulation of current by... 

The 3A zeolites are excellent adsorbents for industrial-scale gas dehydration because of the low energy required for regeneration and ease of operation. A computational study of the dehydration of an industrial feed stream containing ethane and water was performed using an in-house code that included an appropriate equilibrium adsorption isotherm. The validated computational model was used to examine the impact of particle size on the process dynamics and the corresponding pressure drop. The water concentration along the adsorption column was also investigated. To increase the process capacity, the packed adsorption bed was divided into two distinct layers, which were operated with different... 

A number of conformational diseases in humans have been associated with protein/peptide fibrillation known as amyloid. Although extensive studies have been conducted in understanding the molecular basis of amyloid formation, a detailed mechanism is still missing. Experimentally, HEWL (hen egg white lysozyme) has been exploited ubiquitously as a model protein for amyloid fibrillation and drug inhibition. However, computational studies investigating fibril formation of HEWL have been a difficult task to perform mainly due to high stability of lysozymes and the absence of crystal structures of HEWL fibril oligomers. In this study, we have examined various conditions of HEWL amyloid formation... 

The structural and computational studies of a new molybdenum tetracarbonyl complex of 5,14-dihydro-6,17-dimethyl-8,15-diphenyldibenzo[b,i]-[1,4,8,11]tetraazacyclotetradecine, a 14-membered tetraazaannulene macrocyclic ligand, Me2Ph2H2TAA, were carried out by X-ray crystallography and density functional and natural bond orbital (NBO) theories. The complex showed an interesting intermolecular C-H⋯O hydrogen bond which was supported by n → π∗ interaction, forming a one-dimensional extended chain along the b-axis. Interesting intramolecular C-H⋯π and very short σ → π∗ (C-H⋯CO) interactions stabilized the twisted geometry of the coordinated ligand. © 2019 The Royal Society of Chemistry 2019  

The structural and computational studies of a new molybdenum tetracarbonyl complex of 5,14-dihydro-6,17-dimethyl-8,15-diphenyldibenzo[b,i]-[1,4,8,11]tetraazacyclotetradecine, a 14-membered tetraazaannulene macrocyclic ligand, Me2Ph2H2TAA, were carried out by X-ray crystallography and density functional and natural bond orbital (NBO) theories. The complex showed an interesting intermolecular C-H⋯O hydrogen bond which was supported by n → π∗ interaction, forming a one-dimensional extended chain along the b-axis. Interesting intramolecular C-H⋯π and very short σ → π∗ (C-H⋯CO) interactions stabilized the twisted geometry of the coordinated ligand. © 2019 The Royal Society of Chemistry 2019  

We have investigated the piezoelectric response of the hydrogenated graphene oxide (H-G-SiO2) stacks both experimentally and theoretically. The piezoresponse force microscopy method and density-functional theory (DFT) calculations were used to study the piezoresponse effect of this structure from both experimental and computational point of views. A mono-layer graphene, made by chemical vapour deposition method, is deposited on Si/SiO2 substrate and its surface is then functionalized with hydrogen atoms. The vertical piezoresponse, observed by piezoresponse force microscopy, is measured to be about 2146 pC N-1, that is comparable to the reported state of the art piezoelectric materials such... 

A new method for fluorescent microscopy has been proposed. Proposed method uses indirect excitation of fluorophores with nanometer localized illuminating source. Localized source is created at corners of gold nanotriangles which are deposited on glass substrate. Actually the combination of gold nanotriangle (deposited on glass) acts as active substrate (where species will be placed) for our proposed method. The structure will be scanned with a focused beam of laser (or combination of beams). Due to electric field enhancement in corners and edges of nanotringle (because of surface plasmons), third order nonlinear effect will be enhanced accordingly. Enhancement in third order nonlinearity... 

An unusual heterobimetallic bis(triphenylphosphane)(NO2)AgI–CoIII(dimethyl-glyoximate)(NO2) coordination compound with both bridging and terminal –NO2 (nitro) coordination modes has been isolated and characterized from the reaction of [CoCl(DMGH)2(PPh3)] (DMGH2 is dimethylglyoxime or N,N′-di-hydroxybutane-2,3-diimine) with excess AgNO2. In the title compound, namely bis(dimethylglyoximato-1κ2O,O′)(μ-nitro-1κN:2κ2O,O′)(nitro-1κN)bis(triphenyl-phosphane-2κP)cobalt(III)silver(I), [AgCo(C4H7N2O2)2(NO2)2(C18H15P)2], one of the ambidentate –NO2 ligands, in a bridging mode, chelates the AgI atom in an isobidentate κ2O,O′-manner and its N atom is coordinated to the CoIII atom. The other –NO2 ligand... 

Density functional theory (DFT) calculations were performed at the B3LYP level with a 6-311++G(d,p) basis set to systematically explore the geometrical multiplicity and binding strength for complexes formed by Li+, Na+, and K+ with cytidine and 2′-deoxycytidine. All computational studies indicate that the metal ion affinity (MIA) decreases from Li+ to Na+ and K+ for cytosine nucleosides. For example, for cytidine the affinity for the above metal ions are 79.5, 55.2, and 41.8 and for 2′-deoxycytidine, 82.8, 57.4, and 42.2 kcal/mol, respectively. It is also interesting to mention that linear correlations between calculated MIA values and the atomic numbers (Z) of the above metal ions were... 

High-altitude test facilities are usually used to evaluate the performance of space mission engines. The supersonic exhaust diffuser, a main part of high-altitude test facility, provides the required test cell vacuum conditions by self-pumping the nozzle exhaust gases to the atmosphere. However, the plume temperature is often much higher than the temperature the diffuser structure is able to withstand, usually above 2500 K. In this study, an efficient cooling system is designed and analyzed to resolve the thermal problem. A water spray cooling technique is preferred among various existing techniques. Here, a new algorithm is developed for a spray cooling system for a supersonic exhaust... 

Today, the production of energy and electricity is one of the major concerns of mankind. Electricity generation by solar energy is considered as one of the alternatives to fossil fuels. Solar chimneys mechanism is based on a natural phenomenon. In this process the solar energy heat up the earth's surface and the surrounding air. Due to the density difference between cold air and warm air, heated air ascends and causes air circulation. In this study, mathematical modelling of solar chimney and governing equations of this system will be discussed. In order to validate the numerical results, upwind velocity in chimney has been compared with a reliable reference results. As well as, the... 

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...