[QE-users] I have failed to reproduce phonon dispersion of graphene

Tue Mar 30 17:07:27 CEST 2021

Dear Evgeniy,

I use the following  for my graphene dispersion. Please note that the actual coordinates depend on the PSP.

4
0.0 0.0 0.0 150 ! G
0.0000000  -0.577588 0.0 150 ! M
-0.3334706  -0.577588 0.0 150 ! K
0.0 0.0 0.0 1

So the matdyn.x code will automatically set 150 points between the first 2 high-symmetry points and so on.

Cheers,
Vahid

On Mar 30, 2021, at 11:58 AM, Evgenii <eisysoev4 at stud.eltech.ru<mailto:eisysoev4 at stud.eltech.ru>> wrote:

CAUTION: The Sender of this email is not from within Dalhousie.
Dear Vahid,

If we use the default values of the q_in_band_form variables, then how do we find intermediate points between the points of high symmetry, as for example on this site https://www.afs.enea.it/buonocor/graphane-with-phonon.html ? Are intermediate points always needed, we noticed that in some examples they are missing.

Thanks for the help.

Evgeniy Sysoev

30.03.2021, 17:28, "Vahid Askarpour" <vh261281 at dal.ca<mailto:vh261281 at dal.ca>>:
The coordinates of the high-symmetry points in matdyn.in should be in cartesian not crystal because you are specifying q_in_band_form=.true.

Cheers,
Vahid

Vahid Askarpour
Department of physics and atmospheric science
Dalhousie University
Halifax, NS
CANADA

On Mar 30, 2021, at 11:19 AM, Evgenii <eisysoev4 at stud.eltech.ru<mailto:eisysoev4 at stud.eltech.ru>> wrote:

CAUTION: The Sender of this email is not from within Dalhousie.
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.
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