[Wien] Graphene bandstructure
Islam, Md F
islamm at uta.edu
Wed Dec 23 13:22:21 CET 2015
Hi Prof Blaha,
Here is the structure I am using. I tried to be as precise as possible with position coordinates.
I think size of the vacuum is sufficiently large so that supercell-supercell interaction is negligible.
So far what I have got is that with LDA xc if I use 25 x 25 x 1 k-mesh there is a gap at the Fermi
level (which passes through K point) but if I use 30 x 30 x 1 k-mesh, gap closes but DOS is not
zero at the Fermi level (about 0.001/eV). Please let me know if I am doing anything wrong with
this calculation.
Thanks,
Fhokrul
Graphene
P LATTICE,NONEQUIV.ATOMS: 2
MODE OF CALC=RELA unit=bohr
4.647800 4.647800 30.000000 90.000000 90.000000 60.000000
ATOM -1: X=0.00000000 Y=0.00000000 Z=0.50000000
MULT= 1 ISPLIT= 8
C NPT= 781 R0=0.00010000 RMT= 1.3200 Z: 6.0
LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
0.0000000 1.0000000 0.0000000
0.0000000 0.0000000 1.0000000
ATOM -2: X=0.66666667 Y=0.66666667 Z=0.50000000
MULT= 1 ISPLIT= 8
C NPT= 781 R0=0.00010000 RMT= 1.3200 Z: 6.0
LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
0.0000000 1.0000000 0.0000000
0.0000000 0.0000000 1.0000000
12 NUMBER OF SYMMETRY OPERATIONS
-1-1 0 0.00000000
0 1 0 0.00000000
0 0-1 0.00000000
1
-1-1 0 0.00000000
0 1 0 0.00000000
0 0 1 0.00000000
2
-1-1 0 0.00000000
1 0 0 0.00000000
0 0-1 0.00000000
3
-1-1 0 0.00000000
1 0 0 0.00000000
0 0 1 0.00000000
4
0 1 0 0.00000000
-1-1 0 0.00000000
0 0-1 0.00000000
5
0 1 0 0.00000000
-1-1 0 0.00000000
0 0 1 0.00000000
6
0 1 0 0.00000000
1 0 0 0.00000000
0 0-1 0.00000000
7
0 1 0 0.00000000
1 0 0 0.00000000
0 0 1 0.00000000
8
1 0 0 0.00000000
-1-1 0 0.00000000
0 0-1 0.00000000
9
1 0 0 0.00000000
-1-1 0 0.00000000
0 0 1 0.00000000
10
1 0 0 0.00000000
0 1 0 0.00000000
0 0-1 0.00000000
11
1 0 0 0.00000000
0 1 0 0.00000000
0 0 1 0.00000000
12
________________________________________
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 3:29 PM
To: A Mailing list for WIEN2k users
Subject: Re: [Wien] Graphene bandstructure
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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>
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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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