# Exercise 5.1-3

# Quick Questions to 5.1: Dislocations - Basics

| Here are some quick questions:
|  | The answers are sometimes (and possibly only indirectly) contained in the links.

| Draw a schematic lattice fringe picture of a screw dislocations by sketching the planes above and below the dislocation line |
| Produce the dislocation arrangement shown in the picture by Volterra cuts and determine the Burgers vector of the third dislocation.
| Enumerate at least 5 basic properties of dislocations.
| What do you know about the free enthalpy and so on of a dislocation? What is the source of the enthalpy (or energy) of a dislocation? Give a number and discuss consequences for (global and local) equilibrium.
| What is the difference between an edge and a screw dislocation?
| Determine the Burgers vector of the dislocation shown. Here are some hints. |
|  | Try to identify the unit cell first.
|  | The picture shows a projection of a fcc lattice along a <110> direction
|  | The crystal is of the diamond type
|  | If all else fails - use this link
| The thee dislocations shown (in black, red and blue) were made by two successive Volterra cuts. |
|  | Three dislocations = three Burges vectors. How can you determine the three Burgers vectors by the properties of the two cuts?
|  | Can you obtain this basic geometry by just one cut?
|  | If yes, what would kind of Burgers vector would you find in this case for the red line?

| Dislocation loops
|  | Draw a schematic cross -section and a top view of an edge type dislocation loop. Draw in the Burgers vector. Discuss apparent inconsistencies
|  | What is the glide plane of a dislocation loop with edge type character (make a drawing)
|  | Can you draw a screw-type dislocation loop?
|  | Produce an interstitial type and a vacancy type the dislocation loop with the Volterra construction

With frame

5.1.1 Dislocations

5.1.2 Volterra Construction and Consequences

© H. Föll (Defects - Script)