Dear ??, [ Please notice the humble rules how to post to the list:
Affiliation ]
I am not the best expert here, but I presume that you refer to the space
group C_6v, but QE/pw.x only finds the point group C_3v. I am not sure
whether the phonon code could handle the translations (probably not), but
I do not think that this should lead to any serious differences between
the two symmetry groups (in particular since you are using a
more-than-sufficient 'ecutwfc'; well, I do not know whether it would be
better to reduce that and use a value for 'ecutrho' of typical 6-8 times
'ecutwfc'). How large is your deviation from the "reference" (what do you
use as reference?)? Did you consider the LO-TO splitting? You have quite
few k points - and once again, using the lateral shift of k points in a
hexagonal cell "spoils" the symmetries - sorry for repeating this, but it
does not seems to be clear to the wide community.
Greetings from Sunny Paris,
apsi
-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
Ari Paavo Seitsonen / [email protected] / http://www.iki.fi/~apsi/
Ecole Normale Supérieure (ENS), Département de Chimie, Paris
Mobile (F) : +33 789 37 24 25 (CH) : +41 79 71 90 935
On Tue, 12 Apr 2016, wz wrote:
Dear all,
I am trying to calculate the phonon frequency of wurtzite AlN in gamma
point?? i try to use the input files as PHonon/examples/example01/ in
Quantum Espresso. The symmetry of wurtzite AlN is C6v, but in the output of
my calculation, the symmetry is C3v so that the phonon frequency get by my
work do not correspond with that get by reference.
I want to know that if there is a way in quantum espresso to specify the
symmetry? or some other method to get the right symmetry in phonon
calculation?
===================================
pw input
&SYSTEM
ibrav= 4, celldm(1)= 5.8804, nat= 4, ntyp= 2,
celldm(3) = 1.600724
ecutwfc = 160
/
&ELECTRONS
conv_thr = 1.0d-8
mixing_beta = 0.7
/
ATOMIC_SPECIES
Al 26.982 Al.pbesol-n-kjpaw_psl.0.1.UPF
N 14.007 N.pbesol-n-kjpaw_psl.0.1.UPF
ATOMIC_POSITIONS crystal
Al 0.333333343 0.666666687 0.000000000
Al 0.666666627 0.333333313 0.500000000
N 0.333333343 0.666666687 0.381929994
N 0.666666627 0.333333313 0.881929994
K_POINTS automatic
2 2 1 1 1 1
------
ph input
phonons of aln at Gamma
&inputph
tr2_ph=1.0d-14,
prefix='aln',
epsil=.true.,
outdir='/tmp',
fildyn='aln.dyn',
/
0.0 0.0 0.0
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