Dear all QE users,
I am calculating phonon dispersion using two modes of PH module of quantum
espresso. One mode is to split total calculation into calculations of each
irreducible q point (SPLIT), while the other is the GRID calculation as the
demonstrated in the GRID_example, which is to take all the irreducible
representations into consideration. However, the output files shows different
information when I use these two method to calculate phonon frequency with the
same structure and scf input. The main difference is that in the output of GRID
method there is a warning shown below:
##########################################################
Starting wfc are 267 atomic wfcs
Possibly too few bands at point 1 -0.12500 0.12500 0.12500
Possibly too few bands at point 2 0.37500 -0.37500 0.62500
Possibly too few bands at point 3 -0.37500 0.37500 -0.12500
Possibly too few bands at point 4 0.12500 -0.12500 0.37500
…
…
…
Possibly too few bands at point 87 -1.12500 -0.37500 -0.37500
Possibly too few bands at point 88 -0.62500 -0.87500 0.12500
##########################################################
While there is no such information in the output file of SPLIT method.
The input of GRID method for each irreducible representation is shown below
##########################################################
Phonon of K3C60
&inputph
tr2_ph=1.0d-17,
prefix='K3C60',
ldisp=.true.
nq1=2, nq2=2, nq3=2
start_q=2
last_q=2
start_irr=’irr_num’,
last_irr=’irr_num’,
amass(1)=12
amass(2)=39.1
outdir='./',
fildyn='K3C60.dynG',
reduce_io = .true.
/
##########################################################
And the input of GRID method after collecting all the information of each
irreducible representation is
##########################################################
Phonon of K3
&inputph
tr2_ph=1.0d-17,
prefix='K3C60',
ldisp=.true.
nq1=2, nq2=2, nq3=2
recover=.true.,
start_q=2
last_q=2
amass(1)=12
amass(2)=39.1
outdir='./',
fildyn='K3C60.dynG',
reduce_io = .true.
/
##########################################################
And the input of SPLIT method is
##########################################################
Phonon of K3C60
&inputph
tr2_ph=1.0d-17,
prefix='K3C60',
ldisp=.true.
nq1=2, nq2=2, nq3=2
start_q=2
last_q=2
amass(1)=12
amass(2)=39.1
outdir='./',
fildyn='K3C60.dynG',
reduce_io = .true.
/
##########################################################
Why is there the difference information in the output file for the same
structure and scf input? I will appreciate it if anyone could give me any
information about that.
Best regards
Zhishuo Huang
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