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Boltzmann Method for Investigating the Non-Linear Mechanical Behavior of Coarse- Grained Crystals with FCC Network, Exploiting the Effect of Dislocation

Sabetfard, Sajad | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: English
  3. Document No: 53213 (53)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Khoei, Amir Reza; Jahanshahi, Mohsen
  7. Abstract:
  8. In these days world, the increasing growth of Nanotechnology has caused to invent and create new numerical and also computational methods which have more abilities and capabilities for evaluating systems in this scale. Although Some techniques, such as Molecular Dynamics Methods are capable of evaluating nanostructures, lack the ability to simulate large systems of practical size and time scales which is the most important index during the simulation. Therefore, in order to be able to produce an acceptable exact simulation of a large model, simulation of which is limited by the computational cost of the current molecular dynamics methods at hand, Coarse-Graining technique has recently become a very effective and beneficial method which by reducing the numbers of degrees of freedom which it is done by doing reducing the numbers of iterations steps, to development and also increase the ability to simplify models of molecular system, so that the results of models which are simulated in this techniques has less expansivity computational than the original atomistic models. Up until recently, the models which were coarse-grained have only been used to simulate large biomolecules such as proteins, lipids, DNA, and polymers since they consist of massive and complex structures that make them impossible to be modeled by previous molecular methods available. However, in this research, we have focused on applying the Iterative Boltzmann Inversion(IBI) Coarse-Graining(CG) Technique to crystals of metals with FCC network structures in order to be able to simulate larger models of practical size, modeling which is able to consume the time and energy of modeling by the molecular dynamic methods. In this particular technique, the goal is to determine a Coarse-Grained potential in such a way that the target is the radial distribution function of the reference all-atom system, which structurally characterizes the atomistic system, is reproduced. At the beginning of this research, no actual coarse-graining was carried out and the aim was to simply develop an interatomic potential for the all-atom system using the Iterative Boltzmann Inversion method and investigate the efficiency of this newly developed potential in representing the all-atom model simulated using the EAM potential. Due to a few drawbacks of the IBI method such as failing to produce state- independent potentials, we also investigated the influence of the Dislocation in Iterative Boltzmann Inversion Technique to obtain the effect of dislocation on IBI method so that to understand that it is capable to model a system with dislocation or not. In general, the aim of this research is to the extent of the standard IBI method to model a system by the effect of dislocations and also to derive a potential that can be used over various thermodynamic states. Once the effectiveness of the IBI method in producing a pair-wise potential to simulate an all-atom model was adequately studied, coarse-graining was conducted and the mechanical behavior of the all-atom system was compared to that obtained from a coarse-grained system, the potential of which was developed using the IBI method. In the end, the efficiency of this developed potential in simulating larger models were studied
  9. Keywords:
  10. Nanotechnology ; Iterative Boltzmann Inversion ; Coarse Grained Model ; Nanostructure ; Molecular Dynamics ; Crystalline Metals ; Mechanical Behavior ; Nonlinear Behavior

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