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different phonon structure between QE and EPW
Posted: Thu Dec 02, 2021 3:28 pm
by sevenel
Dear all,
I calculate the phonon structure using QE and EPW, and I found that they have a little difference at the Gamma position.
How to deal with it, and if it will have a larger impact when I calculate the mobility?
Another question if I get the negative mobility, is it trustworthy？
Re: different phonon structure between QE and EPW
Posted: Fri Dec 03, 2021 12:04 am
by sevenel
this is my input file
Code: Select all
&inputepw
prefix='GeSe'
outdir='./'
dvscf_dir='../ph/save'
elph=.true.
epbwrite = .true.
epbread = .false.
epwwrite=.true.
epwread=.false.
lpolar = .true.
vme = 'wannier'
use_ws = .true.
wannierize=.true.
nbndsub=32
bands_skipped='exclude_bands = 1-20'
num_iter = 200
dis_froz_max = 3.0
dis_froz_min = -16.0
proj(1)='Ge:s,p'
proj(2)='Se:s,p'
efermi_read = .true.
fermi_energy= -1.5392
fsthick = 100
nstemp = 1
temps = 0.075
degaussw = 0.001
band_plot = .true.
filkf='KPOINTS'
filqf='KPOINTS'
nk1 = 6
nk2 = 6
nk3 = 1
nq1 = 3
nq2 = 3
nq3 = 1
/
Re: different phonon structure between QE and EPW
Posted: Mon Dec 06, 2021 11:19 am
by sponce
Dear sevenel,
The phonon frequency of polar materials is ill defined exactly at q=Gamma.
However it is well defined for q-->0 along a particular direction.
Therefore you can safely remove the q=0 point from your plot and it should look exactly like the one obtained from matdyn.x
You should not get negative mobility (at least the diagonal of the mobility tensor should not be negative).
Off diagonal component (if very small) can be negative.
It also depend if you do drift or Hall mobility. In the case of Hall mobility, it is possible to have negative values depending how you orient your B-field.
Best,
Samuel
Re: different phonon structure between QE and EPW
Posted: Tue Dec 07, 2021 2:40 am
by sevenel
Dear Samuel
Thank you very much for your reply
Best wishes
zhenqing