band structure of graphene

[sergio]

Hello,

I have been trying to run a band structure calculation of graphene surface on VASP 4.6. I optimize the structure first by getting the kpoints, ENCUT, and lattice constant. Then I do a self-consistent calculation to get the charge density. I have the KPOINT file Gamma centered with a mesh of 12 x 12 x 1. Here is the INCAR

SYSTEM =C
restart settings
ISTART = 0
ICHARG = 2
output settings
LCHARG = .TRUE.
LWAVE = .TRUE.

settings for parallel version (ignored in serial run)
NPAR = 1 how many bands in parallel
LPLANE = .TRUE. distribute each wave over processors

Electronic Relaxation 1
ENCUT = 400
PREC = High Medium=default, Low, High; affects ENMAX, mesh, pspot
EDIFF = 1E-06 energy stopping-criterion for electr. iterations
IALGO = 48
NELM = 40
NELMIN = 3
NBANDS = 8
Ionic Relaxation
IBRION = 2
ISIF = 2
NSW = 100 max number of geometry steps
EDIFFG = -1E-02 stopping-criterion for IOM
POTIM = 0.5

DOS related values:
ISMEAR = -5 -4-tet -1-fermi 1=Methfessel/Paxton 1.order
SIGMA = 0.12


I follow this calculation with a non self-consistent run using the charge density from the previous run. Here are the parameters that I change in the INCAR
ICHARG = 11
IBRION = -1
NSW = 0
ISMEAR = 0
SIGMA = 0.05

and here is the KPOINT file for the band structure non self-consistent run.

kpoints of graphene
10 ! 10 intersections
Line-mode
reciprocal
0.6666 0.3333 0 ! K
0 0 0 ! gamma

0 0 0 ! gamma
0.5774 0.5774 0 ! M

0.5774 0.5774 0 ! M
0.6666 0.3333 0 ! K

0.6666 0.3333 0 ! K
0 0 0 ! gamma

The valence bands seem correct but the conduction bands are not. I have tried changing some parameters in the INCAR, like ENCUT, but I still have the same problem. IS there something I'm supposed to add to the INCAR for the conduction bands? Any help will be much appreciated.

<span class='smallblacktext'>[ Edited ]</span>

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