Student Video Visualizing the Energies of Screw Dislocations
POOJA REDDY: Hi. I'm Pooja. And I will be talking to you about how you can visualize the energy of defects, specifically focusing on screw dislocations. So crystals have an underlying lattice structure. But in reality, they're rarely perfect. They usually have mistakes in them which we call defects. A point defect can be a vacancy where an atom is missing from the lattice. And it can also be an interstitial, where there's an extra atom in the lattice. Another type of defect are dislocations, which are linear defects. Here is an example of an edge dislocation. The red arrow here shows a line direction in the defect, which is at the edge of this extra plane here that's in the lattice. Another type of dislocation is a screw dislocation. The blue arrow here shows a line direction of this defect. Here, items on one side are higher than the other. Here, it's lower. And you see this almost spiral shape that forms kind of like a screw. From these pictures you ...