The Effects Of Production Of Screw Dislocations By The External Forces

With the rapid development of technology, the research on crystal has been deepening gradually in recent years since three scientists who are Orowan, Polanyi and Taylor have proposed the concept about crystal dislocations in 1934. The molecular dynamics simulation technology, w hich is an effective method of describing microscopic phenomena on the basis of computer technology and numerical algorithm, is widely used in materials science and condensed matter physics. With the help of two-dimensional Frenkel-Kontorova(FK) model, the research herein focuses on the conditions that can generate screw dislocation under external forces based on the molecular dynamics theory. The structure and the contents of this paper are as follows:The first chapter is intended to introduce the dislocation theory-related knowledge, including its history of development, the basic concept, the basic types as well as the major applications for it. Besides, this chapter also depicts briefly the FK model, and the connection between dislocation and FK model.The second chapter is to study the impact of external driving forces on generating screw dislocation via applying the simple cube model and hexagonal symmetry model, focuses on the effect of the periodic force on screw dislocation. By graphing and analyzing, the results indicate that both the amplitude of external constant force and the amplitude, the frequency of periodic force have effects on the generation of screw dislocation.The third chapter is a summary for the main contents about this paper, as well as a supplementary explanation for future works, which highlights the importance of crystal defects in studying theoretical physics.