[Pw_forum] Evaluation of metallic/non-metallic conduction in carbon nanotubes

[Nicola Marzari]

Hi Steve,


1) example 1 of the espresso distribution shows how to do a band
structure

2) smearing "m-v", temperature around .03 Ry

3) (m,n) nanotubes that have m-n = 0 or a multiple of 3 are metallic.
Very narrow tubes might deviate from this simple rule, that is
obtained by folding of graphene BZ. A lot of groups have
published band structures of SWNTs.

			nicola



Steven Kirk wrote:

> Hello,
> 
> I want to conduct a set of calculations on carbon nanotubes of different 
> diameters and chiralities to establish:
> 
> 1. If they are metallic, i.e. conducting, along the nanotube length
> 2. If they are not metallic, evaluating the band gap
> 
> Do I need to do an PW 'scf' run followed by a PW 'nscf' run? What 
> smearing/occupancy parameters do I need to set (suggested values 
> welcome) ? I have not spotted a clear output of the calculated band gap 
> anywhere in PW's output files, so how can I calculate the band gap from 
> the data given ?
> 
> Many thanks in advance,
> Steve Kirk

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Prof Nicola Marzari   Department of Materials Science and Engineering
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