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|Title:||A new energy minimization method for atomistic simulations|
|Advisor:||Dr. D.R. Metzger, Dr. M. Niewczas|
|Abstract:||<p>A novel energy minimization framework, based on the Dynamic Relaxation technique, is developed to numerically determine the equilibrium of atomic positions in a crystalline lattice containing internal defects and subjected to the external traction.</p> <p>The internal force and stiffness of individual atoms are obtained as derivatives of the potential energy function. The external traction is axially applied on boundary atoms by means of a newly developed periodic symmetry technique, which allows the deformation of the model to be carried out and ensures the stability of the model during the simulation. The damping ratio adjusts the amount of artificial damping introduced into the numerical integration to dissipate the kinetic energy, so that the simulation is more efficient and accurate for various configurations.</p> <p>The relaxation of the model containing a single edge or screw dislocation without the external loading is in line with the experimental observation and theoretical predictions. The external traction does not prevent the dislocation from dissociation, but changes the separation width between partial dislocations after the relaxation.</p> <p>The interactions between two dislocations gliding on the same slip plane are in agreement with the theory. The increase of the height of two dislocations with the opposite Burgers vectors gliding on parallel slip planes leads to the formation of faulted dipoles or perfect stable dipoles. Two opposite screw dislocations on inclined slip planes can annihilate by the mechanism of re-combination and re-dissociation, and the compression along the slip direction increases the critical height of the annihilation.</p> <p>The present approach has created the capability to provide insight into the atomistic mechanisms and processes of the formation of particular structures in crystalline materials.</p>|
|Appears in Collections:||Open Access Dissertations and Theses|
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