Why the hexagonal structure could be harder

16:42the tetrahedral surfaces are flat compared to and before they were sort of at an angle at that 104.5 degree angle. Here they're flat. You're packing more carbon atoms. The bond length in between these carbon atoms is smaller and so the hardness mechanism is because of the resistance to like any form of stress, this thing is going to be harder than cubic diamond. >> Yes. Okay. >> And I have one just brief question on this visual just cuz there's as a layman the other visual difference here and I I understand that we're looking at wurtzite in this example and the key

17:24difference is there's sort of that bottom row right? So you have the sort of all the tetrahedrals packed in the hexagonal prism at the top and then there's just like a bottom row of empty space that kind of closes it out. >> Yeah, well that thing is just going to be repeating over and over. I think they're only showing >> showing one segment section. >> But because it's a crystal it's like going to just keep repeating. >> Makes sense. Just wanted to clarify. >> Yeah, no that's a good question. Now if we think about how this is different from cubic diamond diamond at a grand scale, not just that okay, the fundamental unit is hexagonal rather than cubic. >> Yes. >> That's the first thing. But now let's let's consider like packing a bunch of carbon atoms like spheres in a

18:07in a enclosed space. How would we do that? Well, there's two ways of doing it. On the left is your cubic diamond. >> Mhm. >> Okay? That's the the one that we had seen earlier where the tetrahedrals are in a cubic sort of repeating unit. >> Yes. >> When you do that layers of carbon atoms repeat but they repeat in a ABC ABC >> Mhm. >> ABC kind of manner. Meaning you're going to get one layer of carbon atoms >> Mhm. >> the B layer which is on top is going to fit somewhere in the gaps of that. >> Yep. >> The C layer is going to fit somewhere on the gaps above that but it's going to be slightly offset from the A layer. >> Yeah, yeah, yeah. >> going to get three distinct layers and it'll repeat like that.

18:48>> Yep. >> Okay? >> Yep. >> With hexagonal diamond just because the nature of the geometry, I only need two layers of stacking. It's going to be A then B is going to fit exactly in the gaps but because A is slightly different from the previous A >> Yeah. >> the next layer can just repeat >> Yes. >> the bottom layer. So my stacking is going to go ABABAB instead of ABC ABC >> Yes. And just for folks who may be listening, I just want to put a disclaimer. This is an slightly important episode for visual reference points because it's it's very obvious visually. It's kind of hard to describe. >> Uh it just with audio or or with voice,