Dear Quantum Espresso experts,
I am having trouble calculating the phonon bands of graphene.
First, I took the cif-file of the already relaxed graphite cell from the Materials Project site https://next-gen.materialsproject.org/ and made graphene cell from it by hand.
Then I relaxed the cell obtained with vc-relax and 12x12x1 k-point set.
I used the same parameters to perform a scf calculation:
&CONTROL
calculation='scf'
title='graphene'
prefix='graphene'
verbosity='high'
restart_mode='from_scratch'
nstep=1000
iprint=1
tstress=.true.
tprnfor=.true.
disk_io='default'
pseudo_dir = '/home/mxm2/Desktop/Graphene',
outdir='/home/mxm2/Desktop/Graphene/temp'
/
&SYSTEM
ibrav = 0,
celldm(1)=1.889726,
nat = 2,
ntyp = 1,
ecutwfc = 60.0 ,
ecutrho = 480.0 ,
/
&ELECTRONS
electron_maxstep = 1000,
conv_thr = 1.0d-12 ,
mixing_mode = 'plain' ,
mixing_beta = 0.7d0 ,
/
ATOMIC_SPECIES
C 12.011 C.pz-rrkjus.UPF
ATOMIC_POSITIONS (crystal)
C 0.000000000 0.000000000 0.000861580
C 0.333333000 0.666667000 0.000838420
CELL_PARAMETERS (alat)
2.438515837 -0.000000000 0.000000000
-1.219257919 2.111816662 0.000000000
-0.000000000 -0.000000000 19.995916314
K_POINTS automatic
12 12 1 0 0 0
Then, I run ph.in calculation:
&inputph
recover=.true.
tr2_ph=1.0d-14,
prefix='graphene',
ldisp=.true.
nq1=12,
nq2=12,
nq3=1,
amass(1)=12.011,
outdir='/home/mxm2/Desktop/Graphene/temp',
fildyn='graphene.dyn',
/
My q2r:
&input
fildyn='graphene.dyn',
zasr='simple',
flfrc='graphene.12x12x1.fc'
/
Matdyn input:
&input
asr='simple',
amass(1)=12.011,
flfrc='graphene.12x12x1.fc',
flfrq='graphene.disp.freq'
q_in_band_form=.true.,
/
4 ! number of q-points
0.000 0.000 0.000 10 ! gamma point
0.500 0.000 0.000 10 ! M
0.333 0.333 0.000 10 ! K
0.000 0.000 0.000 1 ! gamma point
Plotband:
graphene.disp.freq
0 1600
graphene.disp.freq.dat
graphene.disp.freq.ps
0
100 0
Why the phonon dispersion does not match the pictures from the papers and for calculations with e.g. 18x18x1 k-point and nq-point sets the output file of graphene.dyn1 look like:
Dielectric Tensor:
************************ 166.332153320312 0.000000000000
166.332275390625************************ 0.000000000000
0.000000000000 0.000000000000 1.116060253916
Effective Charges E-U: Z_{alpha}{s,beta}
atom # 1
-11117471.575740195811 -0.002632206306 0.000000000000
-0.002632205375-11117471.579664016142 0.000000000000
0.000000000000 0.000000000000 -0.003734609171
Also, what is the best way to set the lattice parameters, via Ibrav or CELL_PARAMETERS?
Any help is appreciated.
Best regards,
Evgeniy Sysoev.
_______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list users@lists.quantum-espresso.org https://lists.quantum-espresso.org/mailman/listinfo/users