Sharif Digital Repository

Several potential models such as Sutherland (ST) and square-well (SW) potential models are used for studying the equilibrium and transport properties. Near and above the inversion temperature these potential models fail to predict the second virial coefficient, so they are not applicable at high temperatures. ST and SW potential models have two different branches; one branch is related to the attraction forces and the other to the repulsive forces. Each branch has its own unique parameters, for example parameters of attraction branch are ε/k (the depth of the potential model) and λ (the width of the potential model). Repulsive branch has only one parameter, σ (the molecular diameter).... 

In this study, some properties of metallochlorophylls - compounds produced by replacing Mg2+ in tetrapyrrolic ring of chlorophyll b with divalent ions – of the forth period transit elements of the periodic table have been investigated. Using DFT/B3LYP method and DGDZVP basis set, structures of these compounds were optimized and the energy of electronic levels, Gibbs free energy of formation of complex, contribution of atomic orbitals to formation of molecular orbitals and partial charges in these molecules were computed. The results show that some properties of these complexes cannot be justified by the common theories of complexes. Among these properties is the negligible effect of... 

Ion channels are present in all cell membranes which are the important part of the performances in regulating the flow across the membrane as well as the signaling. We have investigated the water permeation through carbon nanotube (CNT) membranes as a model for the synthetic ion channels, i.e. peptide nanotube channels (PNCs). The effect of different charge configured CNTs which tailored based on these ion channels on the water permeation has been studied. In addition, the temperature dependence of the permeation using statistical models such as continuous time random walk model (CTRW) via molecular dynamics simulation has been investigated. We have found that there is a jump in the... 

In this thesis heat transfer coefficient and temperature distribution of two Non-Newtonian and a Newtonian fluids in stirred vessel are investigated using Computational Fluid Dynamic (CFD). This vessel is agitated with new impeller called MAXBLEND. Non-Newtonian fluids are aqueous solutions of carboxymethyl cellulose 1.5%w/w and xanthan gum 3% w/w and Newtonian fluid is glycerin. This vessel is simulated in laminar regime with Reynolds number less than 14. The results of simulation are compared with correlation proposed by Kawase et al.
Furthermore as a new research for this impeller, the effects of vessel diameter and position of impeller in the vessel on heat transfer coefficient are... 

In this work, by considering the medium effects and adding the long−range interactions to the isolated pair potential, the concept of the extended effective pair potential of the Lennard−Jones (12, 6, 3) has been purposed for dense systems. Due to lack of any information regarding the parameters of this potential for any fluid, the purpose of this work is to introduce a new method to calculate these parameters using experimental pVT data. Since the extended potential of Lennard− Jones (12, 6, 3) is a general function based on which that an equation of state can be derived (equation of state III) predicts many properties of dense systems that no deviation is observed. Also it doesn’t have... 

In 2009, a general equation of state (EOS-III) based on an effective near-neighbor pair interaction of an extended Lennard-Jones (3, 6, 12) type has been introduced as : , where is the compressibility factor, p and ρ stand for pressure and molar density , respectively, T is Temperature , and e, f and g are the temperature dependent coefficient of the equation of state . the Z_th and Z_in are the thermal and internal contributions of pressure in the compressibility factor, respectively. this equation of state gives a good description of all types of nano- and bulk –solid and bulk fluid at entire temperature and pressure ranges for which thee is experimental data. Investigation show that... 

In this work, CO interaction with macroscopic Ni(111) surface and microscopic Nin (n = 2-4) clusters were investigated. First, the CO interaction with various adsorption sites were studied by DFT methods on Ni(111) surface. On the basis of these calculations, hcp site has the strongest interaction with CO adsorbate. Then, the vibrational frequencies of C=O and adsorptive bond on the hcp site were calculated and the results show that anharmonicity of adsorptive bond is more important than C=O bond. Therefore, three potential models are considered for adsorptive bond and the effect of potential models on its thermodynamic properties was investigated. The results show that the effect of... 

In this thesis dependency of surface tension ( ) on temperature (T ) and density (?), for spherical and nearly spherical fluids like argon has been investigated, using an effective Lennard – Jones (12,6) potential along with a new model according to which half of surface molecules are assumed to be in the liquid phase and the other half in the vapor phase, far from the critical point. The obtained result may be expressed as ? ? ? ( The 2 2= +C D C and D parameters are independent of T and ?). Such an investigation has also been done for many fluids, but by using the extended Lennard – Jones (12, 6, 3) function as the effective pair... 

A simple equation of state (EoS) has recently been introduced (J. Phys. Chem. B 2009, 113, 11977–11987) as (Z-1) v^2=e+f⁄ρ+gρ^2, where Z≡pv⁄RT is the compressibility factor, v=1⁄ρ is molar volume, and e, f, and g are temperature dependent parameters. This EoS has been found to be accurate for all types of nano- and bulk- solids and bulk fluids, in the entire temperature and pressure ranges for which experimental data are reported, except for the isotherms within the critical region.
The aim of this work is to investigate the validity of a 3-term expression similar to the mentioned EoS for both thermal and internal contributions to the compressibility factor, separately. Such... 

In this project, the behavior of single strand DNA (ssDNA) that is end-tethred to surface (surface is covered with an layer of mercaptohexane ) through the Monte Carlo simulation has been investigated. To understand this behavior, a ssDNA has been studied through freely jointed chain (FJC) model with electrostatic, base paring, and base-pair stacking interaction. The concentration of sodium chloride salt in solution is 1 mM and the applied surface potential is -1.5 - +0.25 V. Computational results show that the ssDNA chain can have the following configurations: 1) “very closed”, 2) “closed”, and 3) “open” that considering the amount of energy, the mentioned configurations can be compared... 

In this thesis, We have investigated the accuracy of general equation of state ( EoS III ) and linear isotherm regularity ( EoS I ), introduced on 2009 and 1993, respectively, and the Ghatee’s equation of state ( EoS II ) introduced on 2001, for the pvT data and thermodynamic properties of [BMIM][PF6] ionic liquid. We have carried out simulations at first in a narrow range of pressure, namely within 1-3400 atm and in temperature range from 398 K to 1000 K. The results of fitting of EoS I, EoS II and EoS III into the simulations results, leads to R2 > 0.9936, 0.9800 and 0.9949 respectively, for the pressure range of 1-3400 atm and for the temperature range of 398-1000 K. The results of...