Search for: md-simulation
Article Journal of Computational and Theoretical Nanoscience ; Volume 8, Issue 11 , 2011 , Pages 2187-2192 ; 15461955 (ISSN) ; Simchi, A ; Besharati Givi, M. K ; Rajabpour, A ; Sharif University of Technology
Molecular dynamics (MD) simulations were used to study the mechanical behaviour of β-SiC at nano-scale under tensile loading. Effects of loading rate and tensile temperature on the mechanical properties and failure were studied. Modified embedded-atom method (MEAM) potential and Berendsen thermostat were utilized for modelling. Periodic boundary conditions were employed and the behaviour of material was analyzed under three-axial loading condition at which the stress- strain relation was acceptably size independent. It is shown that with increasing the loading rate from 5 m/s to 70 m/s, the failure strain increases without a remarkable change in the stress-strain relationship. The MD...
Article Solid State Communications ; Volume 151, Issue 17 , 2011 , Pages 1141-1146 ; 00381098 (ISSN) ; Motevalli, B ; Montazeri, A ; Ajori, S ; Sharif University of Technology
Carbon nanostructures such as carbon nanotubes (CNTs) and graphene sheets have attracted great attention due to their exceptionally high strength and elastic strain. These extraordinary mechanical properties, however, can be affected by the presence of defects in their structures. When a material contains multiple defects, it is expected that the stress concentration of them superposes if the separation distances of the defects are low, which causes a more reduction of the strength. On the other hand, it is believed that if the defects are far enough such that their affected areas are distinct, their behavior is similar to a material with single defect. In this article, molecular dynamics...
Article Materials Science and Engineering C ; Volume 31, Issue 2 , March , 2011 , Pages 452-457 ; 09284931 (ISSN) ; Ban, E ; Banihashemi, P ; Abdolhosseini Qomi, M. J ; Sharif University of Technology
Carbon nanotubes (CNTs) are excellent candidates for torsional elements used in nanoelectro-mechanical systems (NEMS). Simulations show that after being twisted to a certain angle, they buckle and lose their mechanical strength. In this paper, classical molecular dynamics simulations are performed on single-walled carbon nanotubes (CNTs) to investigate the effects of torsion speed and temperature on CNT torsional properties. The AIREBO potential is employed to describe the bonded interactions between carbon atoms. The MD simulations clearly show that the buckling of CNTs in torsion is a reversible process, in which by unloading the buckled CNT in opposite direction, it returns to its...
Article Polymer - Plastics Technology and Engineering ; Volume 54, Issue 8 , 2015 , Pages 806-813 ; 03602559 (ISSN) ; Naghdabadi, R ; Sharif University of Technology
Taylor and Francis Inc 2015
Nafion membrane encounters many different thermal conditions and mechanical loadings because of its wide range of applications as a proton exchange membrane (PEM). Molecular dynamics simulation of hydrated Nafion at different temperatures is carried out to investigate the alteration of the physical properties of Nafion under uniaxial loading over a wide range of temperatures. According to the simulation results, increase of the temperature reduces the yield stress. The results also show that the polymer chains ordering increases the glass transition temperature and enhances the self-diffusion coefficient of water in hydrated Nafion. Comparisons show that the elastic modulus and viscosity...
Computational modeling of the transverse-isotropic elastic properties of single-walled carbon nanotubes, Article Computational Materials Science ; Volume 49, Issue 3 , 2010 , Pages 544-551 ; 09270256 (ISSN) ; Sadeghi, M ; Naghdabadi, R ; Rafii-Tabar, H ; Sharif University of Technology
Various experimental and theoretical investigations have been carried out to determine the elastic properties of nanotubes in the axial direction. Their behavior in transverse directions, however, has not been well studied. In this paper, a combination of molecular dynamics (MD) and continuum-based elasticity model is used to predict the transverse-isotropic elastic properties of single-walled carbon nanotubes (SWCNTs). From this modeling study, five independent elastic constants of an SWCNT in transverse directions are obtained by analyzing its deformations under four different loading conditions, namely, axial tension, torsion, uniform and non-uniform radial pressure. To find the elastic...
Molecular dynamics simulation and MM-PBSA calculations of sickle cell hemoglobin in dimer form with Val, Trp, or Phe at the lateral contact, Article Journal of Physical Organic Chemistry ; Volume 23, Issue 9 , March , 2010 , Pages 866-877 ; 08943230 (ISSN) ; Akbarzadeh, H ; Parsafar, G. A ; Sharif University of Technology
As the delay time and hence nuclei formation play a crucial role in the pathophysiology of sickle cell disease, MD simulation and molecular mechanics-Poisson-Boltzmann surface area (MM-PBSA) calculations have been performed on three systems of hemoglobin; namely dimer of hemoglobin with valine (Hb S), tryptophan (Hbβ6W), and phenylalanine (Hbβ6F) at β6 position. The structural changes due to these aromatic substitutions are investigated. It is shown that β subunits have significant impact on the differences between a dimer and other crystal structures. Transition from a dimer to polymer for Hb S system affects the donor molecule more than that of the acceptor. In the case of donor and...
Investigation of the interphase effects on the mechanical behavior of carbon nanotube polymer composites by multiscale modeling, Article Journal of Applied Polymer Science ; Volume 117, Issue 1 , March , 2010 , Pages 361-367 ; 00218995 (ISSN) ; Naghdabadi, R ; Sharif University of Technology
In this article, a multiscale modeling procedure is implemented to study the effect of interphase on the Young's modulus of CNT/polymer composites. For this purpose, a three-phase RVE is introduced which consists of three components, i.e., a carbon nanotube, an interphase layer, and an outer polymer matrix. The nanotube is modeled at the atomistic scale using molecular structural mechanics. Moreover, three-dimensional elements are employed to model the interphase layer and polymer matrix. The nanotube and polymer matrix are assumed to be bonded by van der Waals interactions based on the Lennard-Jones potential at the interface. Using this Molecular Structural Mechanics/Finite Element...
Article Journal of Molecular Liquids ; Volume 240 , 2017 , Pages 468-475 ; 01677322 (ISSN) ; Taherkhani, F ; Mehrjouei, E ; Masoumi, A ; Sharif University of Technology
Elsevier B.V 2017
MD simulations were used for investigation on the kinetic formation of Ni-Pd nanoalloys at different simulation times. We have examined excess energies and bond order parameters for initial gas phase compositions including pure Ni, and Pd, and also Ni0.2Pd0.8, Ni0.4Pd0.6, Ni0.6Pd0.4, Ni0.8Pd0.2 concentrations. Excess energies for created Ni-Pd nanoalloys exhibit more instabilities for larger nanoparticles. Also, bond order results demonstrate amorphous structures for all of created nanoclusters. Moreover, number of formed clusters for pure Ni at 5 ns is more than pure Pd nanoclusters and number of formed clusters decreases when Pd is doped in pure Ni nanocluster. © 2017 Elsevier B.V
Article Journal of the Korean Physical Society ; Volume 71, Issue 1 , 2017 , Pages 54-62 ; 03744884 (ISSN) ; Baniasadi, A ; Moradi, M ; Sharif University of Technology
If an ideal membrane for gas separation is to be obtained, the following three characteristics should be considered: the membrane should be as thin as possible, be mechanically robust, and have welldefined pore sizes. These features will maximize its solvent flux, preserve it from fracture, and guarantee its selectivity. Graphene is made up of a hexagonal honeycomb lattice of carbon atoms with sp2 hybridization state forming a one-atom-thick sheet of graphite. Following conversion of the honeycomb lattices into nanopores with a specific geometry and size, a nanoporous graphene membrane that offers high efficiency as a separation membrane because of the ultrafast molecular permeation rate as...
Development of a molecular dynamic based cohesive zone model for prediction of an equivalent material behavior for Al/Al2O3 composite, Article Materials Science and Engineering A ; Volume 679 , 2017 , Pages 116-122 ; 09215093 (ISSN) ; Movahhedy, M. R ; Mahnama, M ; Sohrabpour, S ; Sharif University of Technology
The interfacial behavior of composites is often simulated using a cohesive zone model (CZM). In this approach, a traction-separation (T-S) relation between the matrix and reinforcement particles, which is often obtained from experimental results, is employed. However, since the determination of this relation from experimental results is difficult, the molecular dynamics (MD) simulation may be used as a virtual environment to obtain this relation. In this study, MD simulations under the normal and shear loadings are used to obtain the interface behavior of Al/Al2O3 composite material and to derive the T-S relation. For better agreement with Al/Al2O3 interfacial behavior, the exponential form...
Free energy, configurational and nonextensivity of Tsallis entropy with the size and temperature in colloidal silver nanoparticles in [EMim][PF6] ionic liquid, Article Journal of Molecular Liquids ; Volume 249 , 2018 , Pages 1012-1019 ; 01677322 (ISSN) ; Taherkhani, F ; Sharif University of Technology
Elsevier B.V 2018
Molecular dynamic simulation was performed to calculate the configurational entropy and the free energy for colloidal silver nanoparticles (Ag NPs) in 1-Ethyl-3-methylimidazolium Hexafluorophosphate [EMim][PF6] ionic liquid (IL). Furthermore, the density functional theory (DFT) was used to get the potential interaction between the metal surface and ion in IL. The effect of size and temperature on the configurational entropy and the free energy of colloidal Ag NPs were investigated. Then, it was compared with the gas phase. The Tsallis nonextensivity of entropy was investigated for different sizes of colloidal Ag NPs and it was shown that sub-extensivity of entropy occurs for colloidal Ag...
An atomistic insight into the implications of ion-tuned water injection in wetting preferences of carbonate reservoirs, Article Journal of Molecular Liquids ; Volume 293 , 2019 ; 01677322 (ISSN) ; Badizad, M. H ; Ghatee, M. H ; Ayatollahi, S ; Sharif University of Technology
Elsevier B.V 2019
The efficiency of water flooding methods is known to improve by applying ion-tuned water injection. Although there is a consensus that such improvement happens through reversing reservoir wettability characteristics to more water-wet state, the true impact of ions is still ambiguous among contradictory debates. The well-known molecular dynamics (MD) simulation techniques would shed light on such ambiguities to gain deep atomic-scale understanding of the process. Results from MD simulations show that the presence of Na+ and Cl¯ ions leads to the formation of an electrical double layer in adjacency of calcite surface while Mg2+ ions dominantly make complexes with hydrocarbons throughout the...
Persian Liquorice extract as a highly efficient sustainable corrosion inhibitor for mild steel in sodium chloride solution, Article Journal of Cleaner Production ; Volume 210 , 2019 , Pages 660-672 ; 09596526 (ISSN) ; Ramezanzadeh, M ; Haddadi, S. A ; Bahlakeh, G ; Ramezanzadeh, B ; Mahdavian, M ; Sharif University of Technology
Elsevier Ltd 2019
The Persian Liquorice was introduced as a sustainable corrosion inhibitor with excellent inhibition action for mild steel in sodium chloride solution. Persian Liquorice is a root of Glycyrrhiza glabra including many active compounds like Glycyrrhizin (GL), 18β- Glycyrrhetinic acid (GA), Liquritigenin (LTG), Licochalcone A (LCA), Licochalcone E (LCE), and Glabridin (GLD). The Fourier transform infrared (FT-IR) spectroscopy was utilized to track various active components exist in the Persian Liquorice extract. Electrochemical impedance spectroscopy, potentiodynamic polarization and electrochemical current noise measurements were conducted to investigate the corrosion inhibition role of various...
Article International Journal of Mechanical Sciences ; Volume 165 , 2020 ; Azizi, B ; Nejat Pishkenari, H ; Sharif University of Technology
Elsevier Ltd 2020
An important issue in the study of the nanostructures behaviors is the surface effects, which increases with the increase of the surface-to-volume ratio. Continuum theories are capable of modeling structures at micro and larger scales with enough precision and low computational costs. However, these theories are unable to predict the mechanical properties of nanostructures accurately. On the other hand, due to their high precision, atomistic modeling techniques are extensively employed for the study of systems at nanoscale; however, computational costs of these techniques are relatively high. In this research, we aim to study the vibrational behavior of nanobeams made of three FCC metals;...
Article Journal of Computational Physics ; Volume 219, Issue 2 , 2006 , Pages 770-779 ; 00219991 (ISSN) ; Ejtehadi, M. R ; Everaers, R ; Sharif University of Technology
Academic Press Inc 2006
We derive exact expressions for the forces and torques between biaxial molecules interacting via the RE-squared potential, a recent variant of the Gay-Berne potential. Moreover, efficient routines have been provided for rigid body MD simulations, resulting in 1.6 times speedup compared to the two-point finite difference approach. It has also been shown that the time cost of a MD simulation will be almost equal to a similar MC simulation, making use of the provided routines. © 2006 Elsevier Inc. All rights reserved