Atomic Terraces - Temperature Dependence

Let's investigate a brief mystery. In the video below, we observe the (110) surface of a NiAl compound, viewed through an electron microscope. In the experiment, the researchers changed the temperature of the crystal and watched the atomic terraces on the surface grow and shrink (surfaces of materials are almost never perfectly flat!)

Exercise 8.3.1: Atomic Terrace Mystery
Not Currently Assigned

We see a clear behavior... the terraces increase in area as they increase temperature and decrease in area as they decrease in temperature. Take 2-3 minutes on this exercise. It's tough to consider conceptually, it's OK if you don't get it.

  1. What do you think's going on? Hint - no extrinsic source of atoms leads to the increase of the size of the terraces.