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In the matdyn.in file, the coordinates of the high-symmetry points should be in cartesian not crystal coordinates since you are using q_in_band_form=.true.
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<div class="">Cheers,</div>
<div class="">Vahid</div>
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<div class="">Vahid Askarpour<br class="">
Department of physics and atmospheric science<br class="">
Dalhousie University<br class="">
Halifax, NS<br class="">
CANADA<br class="">
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<blockquote type="cite" class="">
<div class="">On Jan 22, 2021, at 12:56 PM, Roozbeh Anvari <<a href="mailto:roozbeh.anvari@gmail.com" class="">roozbeh.anvari@gmail.com</a>> wrote:</div>
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<span style="font-weight:bold;font-size:12px;" class="">CAUTION:</span> The Sender of this email is not from within Dalhousie.</div>
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Dear Quantum Espresso experts, <br class="">
<br class="">
I am having a trouble calculating the phonon bands of graphene at $K$-point, </div>
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<div class="">I am using NC+LDA and NC+PBE, ecutwfs=60, Ecutrho=400.0, forc_conv_thr=1.0d-6, <br class="">
<br class="">
as you can see in the attached figure, the calculated acoustic and optical eigenvalues are ok at $\Gamma$ and $M$-points, however the calculated value deviates from what it should be at $K$-point:<br class="">
TA and ZA branches are not overlapping at $K$-point, </div>
<div class="">and a strange bump can be seen when ZO approaches $K$-point, <br class="">
<br class="">
I have checked the convergence for K-mesh, Ecutwfs, and Ecutrho, <br class="">
I have also tried increasing the K and q mesh for scf-calculation,<br class="">
using tr2_ph = 1E-14 and alpha_mix(niter)= .1 also does not improve the results,<br class="">
<br class="">
<br class="">
Thank you for your help, </div>
<div class="">Regards, <br class="">
Roozbeh <br class="">
PDF, physics, Queen's university </div>
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<br class="">
Here is the setup I am using, </div>
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step 1, pw.x <br class="">
<br class="">
&CONTROL</div>
<div class=""> ....<br class="">
calculation='scf'<br class="">
forc_conv_thr=1.0d-6, <br class="">
/<br class="">
<br class="">
&SYSTEM<br class="">
ibrav=0, nat = 2, ntyp = 1, <br class="">
ecutwfc = 60.0 , ecutrho = 400.0, ! 480<br class="">
nosym=.true.,<br class="">
occupations='smearing', smearing='cold', degauss=0.02<br class="">
la2F = .true., <br class="">
/<br class="">
<br class="">
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<div class=""> &ELECTRONS<br class="">
startingwfc='random'<br class="">
diagonalization='cg'<br class="">
conv_thr = 1.0e-12<br class="">
mixing_beta = 0.2<br class="">
electron_maxstep=200<br class="">
<br class="">
<br class="">
ATOMIC_SPECIES<br class="">
C 12.011 C.pz-vbc.UPF<br class="">
<br class="">
CELL_PARAMETERS (angstrom) <br class="">
2.428479517 -0.000000605 0.000000000<br class="">
-1.214240282 2.103124989 0.000000000<br class="">
0.000000000 0.000000000 20.000000000<br class="">
<br class="">
ATOMIC_POSITIONS (crystal)<br class="">
C -0.0002315717 0.0002344099 0.4996978700<br class="">
C 0.6664267343 0.3335704066 0.4996978902<br class="">
<br class="">
K_POINTS automatic<br class="">
64 64 1 0 0 0 <br class="">
<br class="">
%--------------------<br class="">
% step 2 ,pw.x <br class="">
%--------------------<br class="">
</div>
<div class=""> same as above except<br class="">
la2F = .false.,<br class="">
K_POINTS automatic<br class="">
32 32 1 0 0 0<br class="">
<br class="">
%--------------------<br class="">
% step 3 , ph.x <br class="">
%--------------------<br class="">
<br class="">
<br class="">
&inputph<br class="">
tr2_ph=1.0d-14, <br class="">
prefix='ml_gr',<br class="">
fildvscf='ml_gredv',<br class="">
amass(1)=12.011,<br class="">
outdir='./tmp',<br class="">
fildyn='ml_gr.dyn',<br class="">
electron_phonon='interpolated',<br class="">
!el_ph_sigma=0.005, <br class="">
!el_ph_nsigma=10,<br class="">
alpha_mix=0.1 <br class="">
diagonalization='cg', <br class="">
trans=.true.,<br class="">
ldisp=.true.,<br class="">
nq1=4 , nq2=4, nq3=1 <br class="">
! nq1=8 , nq2=8, nq3=1 makes no difference <br class="">
/<br class="">
<br class="">
<br class="">
%--------------------<br class="">
% step 4 , q2r.x<br class="">
%--------------------<br class="">
<br class="">
&input<br class="">
zasr='simple',<br class="">
fildyn='ml_gr.dyn', <br class="">
flfrc='gr333.fc', <br class="">
la2F=.true.<br class="">
/<br class="">
<br class="">
<br class="">
%--------------------<br class="">
% step 5 , matdyn.x<br class="">
%--------------------<br class="">
<br class="">
&input<br class="">
asr='simple', <br class="">
amass(1)=12.011,<br class="">
flfrc='gr333.fc', <br class="">
flfrq='gr333.freq', <br class="">
la2F=.true.,<br class="">
dos=.false.<br class="">
q_in_band_form=.true.<br class="">
</div>
/<br class="">
4<br class="">
0 0 0 20<br class="">
0 .5 0 20<br class="">
-0.3333333 0.6666666 0. 20<br class="">
0 0 0 1<br class="">
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