Lecture 2 Flashcards
What if a plane does not intercept with any axes shown?
Shift the plane parallelly so it can intercept with a & b
What kinds of planes do cubic structures have?
Equivalent planes
Why/how are hexagonal crystal directions represented differently from cubic structures?
They have 120° symmetry and have a four-axis coordinate system
What is the algorithm for finding the crystal direction for hexagonal structures (when c component is 0)?
- Vector repositioned to pass through origin
- Read off projections in terms of unit cell dimensions
- Adjust to smallest integer values
- Enclose in square brackets
What is the Miller-Bravais rule?
Sum of the first three indices must be zero:
u + v + t = 0
What is the algorithm for finding the crystal direction for hexagonal structures (when c component is non zero)?
Basal plane is divided into small triangles with a/3 side length
What are prismatic planes?
Vertical planes parallel to the c-axis
Which crystal structures are close packed?
FCC and HCP
What is the FCC packing sequence?
repeated every three layers, ABCABCABC
What is the HCP packing sequence?
repeated every two layers, ABABABAB
When can a stacking fault form?
If a packing sequence does not follow a certain layer
