[Wien] Graphene bandstructure

[Peter Blaha]

The two eigenvalues at K must be identical by symmetry.

If you have a splitting of some meV it means that your structure is 
slightly wrong.

Typical errors: positions of 1/3 and 2/3 must be given in full precision.
  0.3333   is NOT 1/3

Am 22.12.2015 um 20:31 schrieb Islam, Md F:
> Hi Prof Blaha,
>
>      I have got the gap from plotting bandstructure as well as DOS calculations.
> I can see the linear dispersion at the K point just like the way it is suppose to be
> when I plot all the bands in eV range. But if I zoom in at the K point in meV range,
> I can see the gap.
>
>     I don't think there is anything wrong with the structure. I did check all bond lengths,
> angles before I ran the calculations and they are correct. I suspect I may have to adjust
> parameters. I started to see some difference with LDA xc functional with larger k mesh.
>
>
> Thanks,
> Fhokrul
>
>
>
>
> ________________________________________
> From: wien-bounces at zeus.theochem.tuwien.ac.at [wien-bounces at zeus.theochem.tuwien.ac.at] On Behalf Of Peter Blaha [pblaha at theochem.tuwien.ac.at]
> Sent: Tuesday, December 22, 2015 11:35 AM
> To: A Mailing list for WIEN2k users
> Subject: Re: [Wien] Graphene bandstructure
>
> Graphene is metallic by "symmetry", i.e. EF is at a 2-fold eigenvalue at
> the K-point and bands cross with a linear dispersion.
>
>   From where do you know that graphene has a gap in your calculations ??
>
>   From :gap in the scf file or from plotting the bandstructure or ...
>
> It the state at K is not degenerate, you have the wrong symmetry and are
> not doing graphene.
>
> Am 22.12.2015 um 16:51 schrieb Islam, Md F:
>> Hi,
>>
>>        I am trying to do a bandstructure calculation of graphene to check if I can
>> reproduce results discussed in literature (I am using a unit cell of 2 atoms).
>> With spin-orbit coupling, there should be a gap of the order of few micro-eV
>> and without spin-orbit, there should not be any gap at Dirac point. But I am
>> getting a gap of meV even without spin-orbit. I tried both GGA and LDA with
>> very dense mesh but the gap does not close. So I am wondering if anyone
>> have any suggestion about how to do it in Wien2k.
>>
>>
>> Thanks,
>> Fhokrul
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>>
>
> --
> --------------------------------------------------------------------------
> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
> Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
> Email: blaha at theochem.tuwien.ac.at    WIEN2k: http://www.wien2k.at
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-- 
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
Email: blaha at theochem.tuwien.ac.at    WIEN2k: http://www.wien2k.at
WWW:   http://www.imc.tuwien.ac.at/staff/tc_group_e.php
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