QuantumATK Forum
QuantumATK => Scripts, Tutorials and Applications => Topic started by: Twisty on May 3, 2011, 18:24
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Hi,
there goes a problem in structuring fullerene in FCC crystal structure. Steps that I have taken:
1. took fullerene from "database" option
2. then I have made it FCC crystal structure by "Build" option
3. Used ATK-Extended Huckel method for calculating Bandstructure (attached with this post).
4. But it is neither looks like the ref (http://prl.aps.org/abstract/PRL/v67/i15/p2045_1) or reliable.
please help me simulate the band structure of C60 just like Fig 1. of http://prl.aps.org/abstract/PRL/v67/i15/p2045_1
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I just did a very simplistic calculation, and I get similar results to the PRL mentioned. Now, I didn't really take care about the alignment of the C60 relative to the crystal axes, so the symmetry point are clearly different (we see a direct band gap at our L, which would be their X).
As I said, this was quick-and-dirty; I used the Huckel model, non-selfconsistent. I tried both the Cerda graphite and the Hoffman basis sets, and apart from Cerda being slower, the results are qualitatively very similar.
Now, the really interesting part, at least in a historical perspective, is that the original calculation in the PRL took 6 hours on a pretty serious computer (and they had to stick to 2 k-points or else it would take forever). Mine took 15 seconds (Hoffman basis set) on a simple laptop, with 5x5x5 k-points! :)
If you want to be serious about it, one should do it self-consistently and take care to converge in k-points but also interaction range and mesh cut-off, since this is a rather strange "crystal".
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Thanks a lot Prof. Anders Blom.
I have already tried with DFT but it was taking too much time that I have to stop it. However, I think I need to do some atom alignment in the FCC crystal so that its band structure would be similar to the PRL one.
Thanks again sir for your valuable time.