[QE-users] Why is the Dirac point of the pristine graphene above the Fermi level through the calculation with Quantum Espresso?

[宋克楠]

Dear All,
I am running a test calculation for the band structure of the pristine monolayer graphene with 4×4×1
 supercell through Quantum Espresso (QE).
This is my input file.
&CONTROL
 title = 'SLG_441',
 calculation = 'scf',
 restart_mode = 'from_scratch',
 pseudo_dir = './'
/
&SYSTEM
 ibrav = 0,
 nat = 32,
 ntyp = 1,
 ecutwfc = 50,
 ecutrho = 200,
 nbnd = 156,
 occupations = 'smearing',
 degauss = 1d-9,
 smearing = 'gaussian'
/
&ELECTRONS
 electron_maxstep = 100,
 conv_thr = 1.0d-9,
 mixing_mode = 'plain',
 mixing_beta = 0.8d0,
 diagonalization = 'david'
/
&IONS
 ion_positions = 'from_input'
/
&CELL
 cell_dynamics = 'none'
/
ATOMIC_SPECIES
 C 12.0 C.pbe-n-kjpaw_psl.1.0.0.UPF
CELL_PARAMETERS (angstrom)
 9.8400000000 0.0000000000 0.0000000000
 -4.9200000000 8.5216901054 0.0000000000
 0.0000000000 0.0000000000 23.4000000000
ATOMIC_POSITIONS (angstrom)
C 0.0000000000 0.0000000000 11.7000000000
C 1.2300000367 0.7101408633 11.7000000000
C -1.2300000000 2.1304225263 11.7000000000
C 0.0000000367 2.8405633896 11.7000000000
C -2.4600000000 4.2608450527 11.7000000000
C -1.2299999633 4.9709859160 11.7000000000
C -3.6900000000 6.3912675790 11.7000000000
C -2.4599999633 7.1014084423 11.7000000000
C 2.4600000000 0.0000000000 11.7000000000
C 3.6900000367 0.7101408633 11.7000000000
C 1.2300000000 2.1304225263 11.7000000000
C 2.4600000367 2.8405633896 11.7000000000
C 0.0000000000 4.2608450527 11.7000000000
C 1.2300000367 4.9709859160 11.7000000000
C -1.2300000000 6.3912675790 11.7000000000
C 0.0000000367 7.1014084423 11.7000000000
C 4.9200000000 0.0000000000 11.7000000000
C 6.1500000367 0.7101408633 11.7000000000
C 3.6900000000 2.1304225263 11.7000000000
C 4.9200000367 2.8405633896 11.7000000000
C 2.4600000000 4.2608450527 11.7000000000
C 3.6900000367 4.9709859160 11.7000000000
C 1.2300000000 6.3912675790 11.7000000000
C 2.4600000367 7.1014084423 11.7000000000
C 7.3800000000 0.0000000000 11.7000000000
C 8.6100000367 0.7101408633 11.7000000000
C 6.1500000000 2.1304225263 11.7000000000
C 7.3800000367 2.8405633896 11.7000000000
C 4.9200000000 4.2608450527 11.7000000000
C 6.1500000367 4.9709859160 11.7000000000
C 3.6900000000 6.3912675790 11.7000000000
C 4.9200000367 7.1014084423 11.7000000000
K_POINTS automatic
11 11 1 1 1 1
I am using C.pbe-n-kjpaw_psl.1.0.0.UPF pseudopotential with the details below.
Origin: PS Library
Author: ADC 
Generated using "atomic" code by A. Dal Corso v.6.3
Pseudopotential type: PAW 
Functional type: PBE
Non Linear Core Correction
Scalar relativistic
I found that the Dirac point is located 0.027 eV above the Fermi energy level, shown in the figure blow. Obviously, it is not correct.
Is the problem from the pseudopotential?
Would anyone please give me some suggestions on my input file and recommend a proper pseudopotential to me?
Thank you in advance.
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