[Wien] Graphene bandstructure
Laurence Marks
laurence.marks at gmail.com
Wed Dec 23 14:04:54 CET 2015
As a small addendum, you may also need to ensure that the fft size in lapw0
(via case.in0) is a multiple of 6 along a & b to preserve equivalence of
atoms.
---
Professor Laurence Marks
Department of Materials Science and Engineering
Northwestern University
http://www.numis.northwestern.edu
Corrosion in 4D http://MURI4D.numis.northwestern.edu
Co-Editor, Acta Cryst A
"Research is to see what everybody else has seen, and to think what nobody
else has thought"
Albert Szent-Gyorgi
On Dec 23, 2015 06:57, "Peter Blaha" <pblaha at theochem.tuwien.ac.at> wrote:
> a) As expected, something is wrong with your structure.
>
> It should be a hexagonal lattice (H and not P) and the angle gamma
> should be 120 and not 60, and also the positions need to be changed then.
>
> With an "H" lattice, wien2k keeps the symmetry properly and is less
> affected by rounding errors.
>
> b) And secondly, you did not answer, how you got the "gap" (from
> scf-file, output1 or bandstructure or DOS ???)
>
> Forget DOS (there is a smearing parameter set by default !)
>
> when you use a H lattice and meshes which can be divided by 3 (because K
> has 1/3,1/3,0 coordinates and only with a mesh like 3 3 1, 6 6 1, 9 9
> 1, ... the "K"-point is in the mesh), you can use :GAP from scf,
> otherwise NOT. (best is to use a mesh conpatible with 2 and 3, so 6,6,1
> or 12,12,1 ..., because this includes also the M point.
>
>
>
> On 12/23/2015 01:22 PM, Islam, Md F wrote:
> > 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
> >>> _______________________________________________
> >>> Wien mailing list
> >>> Wien at zeus.theochem.tuwien.ac.at
> >>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
> >>> SEARCH the MAILING-LIST at:
> http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
> >>>
> >>
> >> --
> >>
> --------------------------------------------------------------------------
> >> 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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> >>
> >
> > --
> >
> --------------------------------------------------------------------------
> > 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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> >
>
> --
>
> P.Blaha
> --------------------------------------------------------------------------
> 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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