Papers by Keyword: Molecular Simulation

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Authors: Su Ting Li, Yang Dong Hu, Deng Feng Yang
Abstract: To investigate the diffusion of water, Na+ and Cl- in the MFI membrane system (Si/Al = 191), the grand canonical Monte Carlo (GCMC) method and the followed molecular dynamics (MD) simulations were used to predict the water absorption into aluminosilicate zeolite structure under various conditions of pressure and to determine the water and ions diffusion in the MFI membrane at different concentrations. The simulation results are consistent with the experimental data reported in the literature: as the separation proceeds, the salt ions concentration increase in the MFI membrane, and the diffusion coefficient of the water and salt ions decline.
Authors: Ming Hui Zhou, Wen Jie Sun
Abstract: As the mechanical mechanism in interfacial phenomenon, interfacial forces are known as important but difficult to measure experimentally. In recent years, molecular simulation has been rapidly developed to give novel way in inter-molecular forces. In this study, molecular simulation is introduced into wettability and several formulas are presented to model forces and their microscopic effect among water, vapor and quartz phases. A novel dynamic method is proposed to determine the reasonable value of the cutoff distance to calculate the contact angles in vapor-water-quartz systems with and without fluorocarbon surfactants treated using molecular simulation. With other improvement in molecular simulation, the results of the contact angles are closely consistent with the measured data.
Authors: Tong Liu, Min Shan Liu
Abstract: The crack growth behaviors loaded in mode I under strain and stress control at different temperatures were presented in α-Fe by atomistic simulations using LAMMPS code. The interatomic bonds of atoms were characterized using the embedded atom method interatomic potential. The simulation models were built with initial edge crack subjecting to cyclic uniaxial constant strain rate and constant stress. A temperature range from 100 K to 1200 K was considered to probe the influence of the temperature on crack growth. The crack growth mechanism and the radial distribution function (RDF) during crack growth were investigated. The results indicated that the crack propagation mechanisms were sensitive to temperature and the boundary conditions. By proposed image adjusting technology the dislocation slip bands can be more clearly displayed on screen. In order to include the effect of temperature on crack growth, a temperature factor defined as a function of temperature in exponential form was introduced to modify the theoretical expressions based on thermal activation theory. Its coefficient and index can be determined by the RDF peak value obtained from atomistic simulations. For cyclic loading the crack growth process was dependent on both temperature and cyclic loading period in terms of simulations.
Authors: Guan Jun Chang, Yi Xu, Hong Ju Hu, Li Dong Wei, Shang Fei Sun, Hai Yan Sun, Chang Liu, Ye Wei Xu, Xuan Luo, Fang Hua Zhu, Lin Zhang, Run Xiong Lin
Abstract: Based on different aromatic dibromides and diamines, using Material Studio software and molecular simulation method, Poly(imino ketone) (PIK), Poly(imino ketone ketone) (PIKK), Poly(imino imino ketone) (PIIK), Poly(imino imino ketone ketone) (PIIKK), Flourene-PIIK and Naphthyl-PIIK, respectively, were designed as six different structures of polymers. And through the method of molecular mechanics and molecular dynamics the single-molecule polymer chain model and the aggregation-state model with three-dimensional periodic boundary conditions would be built. Theoretically, the established model has been verified availably after optimization based on molecular mechanics and molecular dynamics.
Authors: Zhi Guo Yan, Wang Hui, Ai Guo Xuan, Yuan Xin Wu
Abstract: The first-principle method based on the pseudopotential plane-wave is adopted to analyze O2 adsorption on the LaMnO3 (001) surface. The calculated results indicate that, LaMnO3 presents half-metal properties by calculating the band structure and density of states (DOS). In the MnO6 octahedron, the O-Mn-O bond is mainly covalent, on the contrast, O-La-O bond is mainly ionic. Molecular oxygen can adsorb on the LaMnO3 (001), M2 may be the most favourable adsorption mode. The adsorption mode leads to the formation of .The valence of Mn in the adsorption sites after adsorption of M1 and M2 is Mn3+0.25, Mn3+0.31, respectively. M2 may be the most adsorption mode that can make Pd 0 to shift Pd2+ more quickly in the process of direct synthesis of diphenyl carbonate (DPC) using the catalyst -Pd supported on the LaMnO3.
Authors: Dong Hyun Jung, Dae Jin Kim, Tae Bum Lee, Ja Heon Kim, Seung Hoon Choi
Abstract: We performed grand canonical Monte Carlo simulations on the series of MOFs, that are Metal-Organic Frameworks having various organic linkers and nanocube frameworks, to find out rational design and synthetic strategies toward efficient hydrogen storage materials. The adsorption amounts of hydrogen molecules showed diverse range according to the variation of parameter values. This indicated that the hydrogen adsorption was sensitive to the values of parameters corresponding to the non-bonding interactions. The optimization of the parameters was done to fit the experimental results at 77 K. After the parameterization of the potential function, we adopted this condition to predict the adsorption amount of hydrogen molecules on IRMOF-3, which has NH2 group as the substituent of hydrogen bonded to benzene ring. The calculation results showed good agreement with experimental adsorptions and we analyzed the adsorption sites of each MOF and the relationship between the adsorption characteristics and the hydrogen uptake capacity.
Authors: Xiao Ming Du, Yong Huang, Er Dong Wu
Abstract: Grand Canonical Monte Carlo(GCMC) method was employed to simulate the adsorption properties of molecular hydrogen on NaA zeolite at 40-293 K and pressures up to 10000 kPa in this paper. The results indicated that the adsorption capacity of hydrogen increased with decreasing temperatures and increasing pressures. The highest hydrogen uptake value is 1.54 wt.% at 40 K and 10000kPa. Adsorption temperature has an important effect on adsorption energies and adsorption sites of hydrogen molecules in NaA zeolite. For lower temperature (below 180 K), the oxygen atoms of zeolite framework and extra-framework cations are stable adsorption sites of hydrogen molecules. For the higher temperatures (above 180 K), the oxygen atoms are only stable adsorption sites of hydrogen molecules.
Authors: Ali Kafash Hoshiar, Hamed Raeisi Fard, Mohamad Mehdi Kheirikhah, Hafez Raeisi Fard
Abstract: As our knowledge about Nano grows we can apply Nano Technology in all fields of Science and Engineering. Molecular simulation can be used to simulate the manufacturing process in nano scale. In this paper, simulations in nano scale were investigated in two main reasons: 1- Morphology in Nano-Micro, 2-Simulation based on molecular dynamics. The basic and main aspects of both methods were explored and also a Matlab algorithm will be suggested to modeling the structure and dynamic in nano scale. First, some pieces in cylindrical and cubic forms were simulated and the effects of thermal treatment in different temperatures were investigated in light of this simulation. Second, a model based on molecular dynamics in 2D was developed to find out the effects of force exerted to AFM..
Authors: Lucile Broussous, Matthieu Lépinay, Benoit Coasne, Christophe Licitra, François Bertin, Vincent Rouessac, André Ayral
Abstract: Porous low-k materials used as insulator for interconnection levels in CMOS devices, are easily damaged during the patterning processes. Pore size characterization after material damage is challenging due to the chemical modification induced by the applied process. Numerical simulation of solvent adsorption on silica and functionalized silica surfaces was used to improve material pore size determination by ellipso-porosimetry, taking into account the modifications of surface/solvent interactions.
Authors: Qiang Yang, Xiao Ping Wen, Chao Ming Sun, Guang Ping Tang
Abstract: The adsorption mechanisms of silicone rubber (SR)-stainless steel (SS) interfacial system and silicone rubber-HMX interfacial system were studied by molecular simulation method in the present paper. The molecular simulation results revealed that silicone rubber-stainless steel interface has obvious adsorption effect, while silicone rubber-HMX interface has certain adsorption effect. The systematic potential energy calculation results revealed that coulomb interaction and van de waals interaction might be the major microscopic adsorption mechanism for silicone rubber-stainless steel interfacial system and silicone rubber-HMX interfacial system.
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