| Summary: | 碩士 === 國立成功大學 === 機械工程學系專班 === 93 === Coarse Grained Molecular Dynamics (CGMD) is a technique for simulation extended from Molecular Dynamics (MD). It captures the important atomistic effects with fewer nodes instead of atoms so that CGMD can not only effectively save more computational cost than MD but it also can vary its scale to describe the system more appropriate in multi-scales simulation.
The concept of CGMD utilizes Finite Element Method (FEM) to reduce the number of atoms. And the equations of motion are derived directly from MD through a statistical coarse graining procedure so that the different scales are run concurrently with the same model in multi-scale simulation. Therefore, this allows a seamless coupling of length scales.
Despite its having above advantages, CGMD model is still in its infant. Especially in dealing with the potential function, it still exist some limitations. Therefore, except developing the CGMD theory, two approaches for atom/node transformation of potential function will be discussed in this thesis. First approach is taking advantage of Taylor series to describe the model; and second is describing the model by finding the “new parameters of material”. As the results of simulation, all of these two approaches have good performance in equilibrium state. However, considering the tension, torsion, and compression case, it still has some limitations in CGMD method. Therefore, this paper will explore the cause of limitation and discuss the way to improve the simulation base on theory and results of simulation as well.
In conclusion, the determination of appropriate potential function for describing the CGMD model is the key to solve the limitations. As long as the potential function can well describe the behavior of node, CGMD can transform the calculations from atoms to nodes successfully. Therefore, CGMD will not only have the ability to simplify the MD but it also can accurate describe specific materials on length scales spanning from the microscopic to mesoscopic scale.
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