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A Combined Molecular Dynamics-Coarse Graining Technique for Modeling the Mechanical Behavior of Crystalline Nano-Structures

Mohammad Reza, Kimia | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: English
  3. Document No: 54676 (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 the area of material studies, the atom structure models are the basis of all simulations and methods. With improvements in computers power, these models have become more consistent with experimental results. New theoretical methods combined with supercomputers assist to an understanding with detail and accuracy of material behavior at the atomic scale that leads to develop of the Computational Materials Science. Recently, developments in fields such as quantum mechanics, statistical physics, solid-state physics, quantum chemistry, computer science and graphics, allowed for faster computing which leads a powerful tool for material calculations and designs. New computer applications allow simulations, construction and design of new materials, and prediction the properties of new materials before preparation experiments. Molecular dynamics (MD) is a computer simulation method for studying the physical and mechanical behaviors of atoms and molecules. The atoms and molecules interactions limited for a fixed period time which gives a view of the dynamic evolution of the system. In common versions, the trajectories of atoms and molecules are determined by numerically solving Newton's equations of motion where forces between the particles and their potential energies are determined by using interatomic potentials or molecular mechanics force fields. The classical methods usage for modeling the Nanoscale systems are not practical because of the great surface effects that appear at small dimensions. Implementing more accurate methods results in extend computations as these methods are highly quantum and atomistic models dependent and they can be employed for very small sizes in short time periods. In order to speed up the molecular dynamics (MD) simulations coarse-graining (CG) samples are modeled in this research. The procedure consists of establishing a zone between the main structure’s atoms and grains comprising the CG model and modified the systems parameters such that the original and the CG models reach identical physical parameters. The accuracy and speed of this model is investigated by accomplishing various statically and dynamically simulations. In this study the boundary between the original and the CG model parts will be modeled in order to improve the accuracy and speed of the simulation in parts (e.g., existence of discontinuities or some holes) that only CG method cannot model the real state of stresses in these parts
  9. Keywords:
  10. Molecular Dynamics ; Mechanical Behavior ; Multi-Scale Analysis ; Nanostructure ; Coarse Grain Molecular Dynamic ; Coarse Grained Model

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