Cross slip problem in f.c.c crystal

[rubee]

Homework Statement

Because the book gives me little information about the cross slip. So I can't handle the basic problem below. I appreciate that you can give me some hints or suggestion.
An f.c.c crystal is deforming by motion of disslocations on the (a/2)[101](11-1) (I use minus instead of bar) slip system.
Q1: In order for the dislocations to cross slip, what would be their orientation on the (11-1) plane?
Q2: Onto what plane could these dislocations cross slip?
Q3: What would the orientation of the dislocations on the (a/2)[101](11-1) slip system have to be in order for the dislocations to be in pure edge orientation?
(Sorry about the other simplified symbols instead because of the imput problem)

Homework Equations

The Attempt at a Solution

Since dislocations can only slip on planes containing both tangent vector t and Burgers vector b, only dislocations in screw orientation can cross slip.

 

[Valkarie]

Q1: The dislocations must be in screw orientation on the (11-1) plane. Q2: The dislocations can cross slip onto the (1-1-1) plane. Q3: To be in pure edge orientation, the dislocations must be oriented along the [100] direction on the (a/2)[101](11-1) slip system.

 

[Mene]

On the (11-1) plane, the dislocations would be in pure screw orientation.
They could cross slip onto the (a/2)[101](11-1) slip system, which would require a change in the Burgers vector from b to a/2[101].
To be in pure edge orientation, the dislocations would need to be perpendicular to the slip direction, so on the (a/2)[101](11-1) slip system, they would need to be in the <101> direction.