Let's see if we can, based upon what we've just learned, identify what possible slip systems there might be in an FCC crystal if I give you a combination of a plane in the direction. The first example, what we're going to do is to calculate whether or not this is a slip system that is viable with respect to the FCC material, and if it isn't, why isn't it? So the first one we're going to look at are the series of what I'm referring to as slip systems. Remember, a slip system defines a slip plane and it defines a slip direction. Okay, so let's take a look at the first one, and the first one tells me that I have slip in the direction of 111 on the 101 bar plane. Now that happens to be a slip system but it is not a slip system for face-centered cubic. Remember that in terms of face-centered cubic, it's going to be on the 111 plane, not the 111 direction, and it's going to be in the 110 direction, not the 101 bar plane. So that's the slip plane, that's the slip direction as given by the symbols that I've put up here, and as a consequence this is not slip in FCC. It turns out that it's actually slip in body-centered cubic. And remember, when we were talking about these ideas of slip systems, in the section where we were describing close packed planes and close packed directions in BCC and FCC, we recognize that the BCC has a densely packed plane of 110. Now we'll look at the second slip system that we are to examine, and what we see is that we have the slip plane and it's correctly identified as a 111 for face-centered cubic. And when we look at directions it looks like it might be a good direction, but when we look at this particular direction, what we see is the magnitude is going to be related to a zero, not a zero over two. So it turns out that that's actually not the right vector. This vector takes us not to the closest atom position but one beyond that. So for example, if we are at a position that's on the corner of the cube, this vector takes us to the other corner on that particular face. We need to go to the position that's halfway between those, and so consequently this is not going to be a vector for the FCC materials. Now, the thing that we want to pay attention to is not only is this vector too large, but we need to think about why it might be considered to be too large. What we know about vectors is the fact that it tells us, the vector tells us how far we have to go through the slipping process. If we're doubling the slipping process we would assume that there was going to be an increase in the amount of force that we would have to apply, in order to move those two atom positions. And consequently, it would have a higher, that would be a higher energy process. So what we actually find is that the energy of the dislocation is going to be related to the magnitude of the Burgers vector as given by the equation on the slide. So when you put in that magnitude for the vector a0, we find out that it's larger than that which is associated with a0 over 2. So this again is not a valid slip system for the FCC material. Okay, let's go on to our third. When we look at the third, what we see is we have the correct slip plane and we have a good slip direction, because it is again on a 101 direction, on a 111 plane and the magnitude, this time, is a0 over 2. So this looks pretty good, but before we conclude what we need to do is actually plot the direction in the plane, and see if in fact the slip direction actually lies on the slip plane. When we do that, what we see is there is the 111 plane. Those two red spots represent the direction of closest approach, given by the vector a0 over 2, 1 bar 01. So consequently, because that vector does not lie on that slip plane, this is not a possible slip system for this FCC crystal. Now looking at the last, what we have again is a slip plane and a slip direction, which are correct. And now we need to see how they fit onto our planes in directions inside of our cube. And what we see, there is the 1 bar 1 plane, and on that 1 bar 11 plane, we have the vector, which is given by 101. So consequently, because the slip plane contains the slip direction, this then becomes a possible slip system. Thank you.