Why is the density of states at Fermi level output by EPW inconsistent with that calculated by dos.x?

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Moderator: hlee

dhw
Posts: 16
Joined: Thu Dec 03, 2020 7:46 am
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Why is the density of states at Fermi level output by EPW inconsistent with that calculated by dos.x?

Hello everyone, I have recently come across a problem, and I hope to get some advice from the seniors.
The problem is that the density of states at the Fermi level calculated using the dos. X package does not agree with the epw.x output. The Fermi levels in epw.x calculations are not very different.
The output of the dos.x is:
1.62 states/spin/eV/Unit Cell at Ef= 6.1639 eV
The output of epw.x is :
DOS = 1.350528 states/spin/eV/Unit Cell at Ef= 6.175629 eV
Because the Ef has a liitle differently that it's normal to have different DOS values.
However, it can be seen from the state density diagram that the state density value near the Fermi level is larger than the above 1.62. How can epw.x output a smaller state density value?

Code: Select all

``````   5.445  0.5961E+01  0.3032E+02
5.450  0.5784E+01  0.3035E+02
5.455  0.5271E+01  0.3037E+02
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5.465  0.4454E+01  0.3042E+02
5.470  0.3996E+01  0.3044E+02
5.475  0.3522E+01  0.3046E+02
5.480  0.3271E+01  0.3047E+02
5.485  0.3501E+01  0.3049E+02
5.490  0.4335E+01  0.3051E+02
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5.500  0.5366E+01  0.3056E+02
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5.515  0.2408E+01  0.3061E+02
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5.535  0.1855E+01  0.3065E+02
5.540  0.1778E+01  0.3066E+02
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5.585  0.2243E+01  0.3079E+02
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7.305  0.5201E+01  0.3944E+02
7.310  0.6338E+01  0.3948E+02
7.315  0.7208E+01  0.3951E+02
7.320  0.7900E+01  0.3955E+02
7.325  0.8324E+01  0.3959E+02
7.330  0.8238E+01  0.3963E+02
7.335  0.7950E+01  0.3967E+02
7.340  0.7688E+01  0.3971E+02
7.345  0.7252E+01  0.3975E+02
7.350  0.6618E+01  0.3978E+02
7.355  0.5842E+01  0.3981E+02
7.360  0.4999E+01  0.3984E+02
7.365  0.4556E+01  0.3986E+02
7.370  0.4875E+01  0.3988E+02
7.375  0.5627E+01  0.3991E+02
7.380  0.6610E+01  0.3994E+02
7.385  0.8090E+01  0.3998E+02
7.390  0.9626E+01  0.4003E+02
7.395  0.1017E+02  0.4008E+02
7.400  0.9466E+01  0.4013E+02
7.405  0.8178E+01  0.4017E+02
7.410  0.7170E+01  0.4021E+02
7.415  0.7107E+01  0.4024E+02
7.420  0.8079E+01  0.4028E+02
7.425  0.9361E+01  0.4033E+02
7.430  0.1015E+02  0.4038E+02
7.435  0.1038E+02  0.4043E+02
7.440  0.1025E+02  0.4048E+02
7.445  0.9752E+01  0.4053E+02
7.450  0.8736E+01  0.4058E+02
7.455  0.7271E+01  0.4061E+02
7.460  0.5952E+01  0.4064E+02
7.465  0.5656E+01  0.4067E+02
7.470  0.6728E+01  0.4070E+02
7.475  0.8243E+01  0.4075E+02
7.480  0.8914E+01  0.4079E+02
7.485  0.8652E+01  0.4083E+02
7.490  0.8378E+01  0.4088E+02
7.495  0.8834E+01  0.4092E+02
7.500  0.9761E+01  0.4097E+02
7.505  0.1005E+02  0.4102E+02
7.510  0.9065E+01  0.4106E+02
7.515  0.7586E+01  0.4110E+02
7.520  0.6876E+01  0.4114E+02
7.525  0.6945E+01  0.4117E+02
7.530  0.7025E+01  0.4121E+02
7.535  0.7263E+01  0.4124E+02
7.540  0.7973E+01  0.4128E+02
7.545  0.8212E+01  0.4132E+02
7.550  0.7497E+01  0.4136E+02
7.555  0.7107E+01  0.4140E+02
7.560  0.7878E+01  0.4144E+02
7.565  0.9027E+01  0.4148E+02
7.570  0.9517E+01  0.4153E+02
7.575  0.8972E+01  0.4157E+02
7.580  0.7787E+01  0.4161E+02
7.585  0.6766E+01  0.4165E+02
7.590  0.6178E+01  0.4168E+02
7.595  0.5733E+01  0.4171E+02
7.600  0.5481E+01  0.4173E+02
7.605  0.5681E+01  0.4176E+02
7.610  0.6109E+01  0.4179E+02
7.615  0.6201E+01  0.4182E+02
7.620  0.5735E+01  0.4185E+02
7.625  0.5155E+01  0.4188E+02
7.630  0.4900E+01  0.4190E+02
7.635  0.4850E+01  0.4193E+02
7.640  0.4810E+01  0.4195E+02
7.645  0.4868E+01  0.4197E+02
7.650  0.5052E+01  0.4200E+02
7.655  0.5091E+01  0.4203E+02
7.660  0.4652E+01  0.4205E+02
7.665  0.3834E+01  0.4207E+02
7.670  0.3169E+01  0.4208E+02
7.675  0.3140E+01  0.4210E+02
7.680  0.3896E+01  0.4212E+02
7.685  0.5053E+01  0.4214E+02
7.690  0.5885E+01  0.4217E+02
7.695  0.5916E+01  0.4220E+02
7.700  0.5239E+01  0.4223E+02
7.705  0.4585E+01  0.4225E+02
7.710  0.4778E+01  0.4228E+02
7.715  0.5644E+01  0.4230E+02
7.720  0.6078E+01  0.4233E+02
7.725  0.5743E+01  0.4236E+02
7.730  0.5488E+01  0.4239E+02
7.735  0.5836E+01  0.4242E+02
7.740  0.6507E+01  0.4245E+02
7.745  0.7147E+01  0.4249E+02
7.750  0.7734E+01  0.4253E+02
7.755  0.8249E+01  0.4257E+02
7.760  0.8393E+01  0.4261E+02
7.765  0.8148E+01  0.4265E+02
7.770  0.8022E+01  0.4269E+02
7.775  0.8314E+01  0.4273E+02
7.780  0.8823E+01  0.4278E+02
7.785  0.9628E+01  0.4282E+02
7.790  0.1094E+02  0.4288E+02
7.795  0.1222E+02  0.4294E+02
7.800  0.1280E+02  0.4300E+02
7.805  0.1273E+02  0.4307E+02
7.810  0.1230E+02  0.4313E+02
7.815  0.1182E+02  0.4319E+02
7.820  0.1170E+02  0.4325E+02
7.825  0.1171E+02  0.4331E+02
7.830  0.1152E+02  0.4336E+02
7.835  0.1142E+02  0.4342E+02
7.840  0.1149E+02  0.4348E+02``````
Could you please tell me what the situation is? I use the same k point and the same Gaussian spread. Sincere thanks.

hlee
Posts: 332
Joined: Thu Aug 03, 2017 12:24 pm
Affiliation: The University of Texas at Austin

Re: Why is the density of states at Fermi level output by EPW inconsistent with that calculated by dos.x?

Dear dhw:

I don't know about your computational details, but you can obtain the different DOSs depending on your interpolation quality.

Sincerely,

H. Lee

hpaudya1
Posts: 111
Joined: Tue Mar 21, 2017 7:11 pm
Affiliation:

Re: Why is the density of states at Fermi level output by EPW inconsistent with that calculated by dos.x?

Hi dhw,

Can you do a DOS calculation using QE with the mp smearing using the same smearing value from EPW? Please note that the unit of the smearing used in QE is Ry while in EPW is eV.

Best,
Hari Paudyal

dhw
Posts: 16
Joined: Thu Dec 03, 2020 7:46 am
Affiliation: none

Re: Why is the density of states at Fermi level output by EPW inconsistent with that calculated by dos.x?

hlee wrote:
Thu Jan 13, 2022 9:20 pm
Dear dhw:

I don't know about your computational details, but you can obtain the different DOSs depending on your interpolation quality.

Sincerely,

H. Lee
Hi H. Lee
How do I do this interpolation? Use EPW interpolation?

dhw
Posts: 16
Joined: Thu Dec 03, 2020 7:46 am
Affiliation: none

Re: Why is the density of states at Fermi level output by EPW inconsistent with that calculated by dos.x?

hpaudya1 wrote:
Thu Jan 13, 2022 10:04 pm
Hi dhw,

Can you do a DOS calculation using QE with the mp smearing using the same smearing value from EPW? Please note that the unit of the smearing used in QE is Ry while in EPW is eV.

Best,
Hari Paudyal
Hi, Hari Paudyal
I've switched units, and the two values are the same.

dhw
Posts: 16
Joined: Thu Dec 03, 2020 7:46 am
Affiliation: none

Re: Why is the density of states at Fermi level output by EPW inconsistent with that calculated by dos.x?

Hi, everyone
Question supplement: In the above question, my calculations use the same broadening, and the bands fitted by epW call wannier90.x are consistent. And its Fermi energy level can basically match (as mentioned above), but it is not clear why the DOS output of EPW is inconsistent.
Thanks,everyone

hpaudya1
Posts: 111
Joined: Tue Mar 21, 2017 7:11 pm
Affiliation:

Re: Why is the density of states at Fermi level output by EPW inconsistent with that calculated by dos.x?

Hi dhw,
I've switched units, and the two values are the same.
You mean, with the same value of the smearing, the DOS with QE and EPW matched?

If not, could you please share your scf,in, nscf.in (for the dos calculation using QE) and scf.in, nscf.in, and epw.in (for the epw calculation) files?

Best,
Hari

dhw
Posts: 16
Joined: Thu Dec 03, 2020 7:46 am
Affiliation: none

Re: Why is the density of states at Fermi level output by EPW inconsistent with that calculated by dos.x?

hpaudya1 wrote:
Sun Jan 16, 2022 5:05 am
Hi dhw,
I've switched units, and the two values are the same.
You mean, with the same value of the smearing, the DOS with QE and EPW matched?

If not, could you please share your scf,in, nscf.in (for the dos calculation using QE) and scf.in, nscf.in, and epw.in (for the epw calculation) files?

Best,
Hari

Hello Hari:
Yes. The two values are the same.
And the inputfile as follow:

scf,in, nscf.in (for the dos calculation using QE):
SCF.IN:

Code: Select all

``````&CONTROL
calculation='scf',
disk_io='low',
prefix=' ',
pseudo_dir=' ',
outdir='./outdir',
verbosity='low',
tprnfor=.true.,
tstress=.true.,
forc_conv_thr=4.0d-4
etot_conv_thr=1.0d-8
/
&SYSTEM
!input_dft='vdw-df2-b86r',
ibrav = 4,
A =
C =
nat= 7, ntyp= 3,
!    assume_isolated = '2D'
occupations = 'smearing', smearing = 'cold', degauss = 1.0d-2,
!	occupations = 'tetrahedra'
ecutwfc = 50,
ecutrho = 500,
nbnd = 55
/
&ELECTRONS
electron_maxstep = 100,
conv_thr = 1.0d-10
mixing_mode = 'plain',
mixing_beta = 0.8d0,
!    diagonalization = 'cg',
/
&IONS
ion_dynamics='bfgs',
/
&CELL
cell_dofree='2Dxy',
/
ATOMIC_SPECIES

ATOMIC_POSITIONS (crystal)

K_POINTS {automatic}
18 18 1 0 0 0
``````
NSCF.IN:

Code: Select all

``````&CONTROL
calculation='nscf',
disk_io='low',
prefix='',
pseudo_dir='',
outdir='./outdir',
verbosity='low',
tprnfor=.true.,
tstress=.true.,
forc_conv_thr=4.0d-4
etot_conv_thr=1.0d-8
/
&SYSTEM
!input_dft='vdw-df2-b86r',
ibrav = 4,
A =
C =
nat= 7, ntyp= 3,
!    assume_isolated = '2D'
occupations = 'smearing', smearing = 'cold', degauss = 1.0d-2,
!	occupations = 'tetrahedra'
ecutwfc = 50,
ecutrho = 500,
nbnd = 55
/
&ELECTRONS
electron_maxstep = 100,
conv_thr = 1.0d-10
mixing_mode = 'plain',
mixing_beta = 0.8d0,
!    diagonalization = 'cg',
/
&IONS
ion_dynamics='bfgs',
/
&CELL
cell_dofree='2Dxy',
/
ATOMIC_SPECIES

ATOMIC_POSITIONS (crystal)

K_POINTS {automatic}
60 60 1 0 0 0
``````
DOS.IN:

Code: Select all

``````&dos
outdir='./outdir/'
prefix=' '
bz_sum='smearing'
ngauss=0
degauss=0.000735              !gaussian broadening, Ry (not eV!)
Emin=-10.0                    !(eV)
Emax=10.0                     !(eV)
DeltaE=0.005                  !(eV)
fildos='DOS.dat'
/
``````
The scf.in, nscf.in, and epw.in (for the epw calculation) files:
SCF.IN:

Code: Select all

``````&CONTROL
calculation='scf',
disk_io='low',
prefix=' ',
pseudo_dir=' ',
outdir='./outdir',
verbosity='low',
tprnfor=.true.,
tstress=.true.,
forc_conv_thr=4.0d-4
etot_conv_thr=1.0d-8
/
&SYSTEM
!input_dft='vdw-df2-b86r',
ibrav = 4,
A =
C =
nat= 7, ntyp= 3,
!    assume_isolated = '2D'
occupations = 'smearing', smearing = 'cold', degauss = 1.0d-2,
!	occupations = 'tetrahedra'
ecutwfc = 50,
ecutrho = 500,
nbnd = 55
/
&ELECTRONS
electron_maxstep = 100,
conv_thr = 1.0d-14
mixing_mode = 'plain',
mixing_beta = 0.8d0,
!    diagonalization = 'cg',
/
&IONS
ion_dynamics='bfgs',
/
&CELL
cell_dofree='2Dxy',
/
ATOMIC_SPECIES

ATOMIC_POSITIONS (crystal)

K_POINTS {automatic}
18 18 1 0 0 0
``````
NSCF.IN:

Code: Select all

``````&CONTROL
calculation='nscf',
disk_io='low',
prefix=' ',
pseudo_dir=' ',
outdir='./outdir',
verbosity='low',
tprnfor=.true.,
tstress=.true.,
forc_conv_thr=4.0d-4
etot_conv_thr=1.0d-8
/
&SYSTEM
!input_dft='vdw-df2-b86r',
ibrav = 4,
A =
C =
nat= 7, ntyp= 3,
!    assume_isolated = '2D'
occupations = 'smearing', smearing = 'cold', degauss = 1.0d-2,
!	occupations = 'tetrahedra'
ecutwfc = 50,
ecutrho = 500,
nbnd = 55
/
&ELECTRONS
electron_maxstep = 100,
conv_thr = 1.0d-10
mixing_mode = 'plain',
mixing_beta = 0.8d0,
!    diagonalization = 'cg',
/
&IONS
ion_dynamics='bfgs',
/
&CELL
cell_dofree='2Dxy',
/
ATOMIC_SPECIES

ATOMIC_POSITIONS (crystal)

K_POINTS crystal
144
0.00000000  0.00000000  0.00000000  6.944444e-03
0.00000000  0.08333333  0.00000000  6.944444e-03
0.00000000  0.16666667  0.00000000  6.944444e-03
0.00000000  0.25000000  0.00000000  6.944444e-03
0.00000000  0.33333333  0.00000000  6.944444e-03
0.00000000  0.41666667  0.00000000  6.944444e-03
0.00000000  0.50000000  0.00000000  6.944444e-03
0.00000000  0.58333333  0.00000000  6.944444e-03
--More--(19%)
``````
EPW.IN:

Code: Select all

``````&inputepw
prefix      =  ''
!  amass(1)    = ,
!  amass(2)    = ,
outdir      = './outdir/'
ep_coupling = .true.
elph        = .true.
kmaps       = .false.
epwwrite = .true.
wannierize  = .true.
!  num_iter    = 0
dis_froz_min= 3.1138
dis_froz_max= 8.1138
proj(1) = ''
!  proj(2) = ''
!  proj(3) = ''
wdata(1) = 'Begin Kpoint_Path'
wdata(2) = 'G 0.00 0.00 0.00   M 0.00 0.50 0.00'
wdata(3) = 'M 0.00 0.50 0.00   K 0.333 0.333 0.00'
wdata(4) = 'K 0.333 0.333 0.0  G 0.00 0.00 0.00'
wdata(5) = 'End Kpoint_Path'
wdata(6) = 'bands_plot = .true.'
wdata(7) = 'bands_num_points = 55'
wdata(8) = 'guiding_centres = .true.'
wdata(9) = 'dis_num_iter = 5000'
bands_skipped = 'exclude_bands = 1:23'

system_2d=.true.
etf_mem     =  1
nbndsub     =  24,
iverbosity  = 2
eps_acustic = 2.0    ! Lowest boundary for the phonon frequency
ephwrite    = .false. ! Writes .ephmat files used when Eliasberg = .true.
fsthick     = 0.32  ! eV
degaussw    = 0.01 ! eV
nsmear      = 1
nqsmear     = 1
delta_smear = 0.01 ! eV
degaussq     = 0.5 ! meV
nqstep       = 500
!  fermi_energy =  6.1639
! eliashberg  = .true.
! laniso = .true.
! limag = .true.
conv_thr_iaxis = 1.0d-4
max_memlt = 3.0d0
!  asr_typ = 'crystal'
delta_approx = .true.,
!  elecselfen = .true.,
phonselfen = .true.,
a2f = .true. ,
wscut = 1.0   ! eV   Upper limit over frequency integration/summation in the Elisashberg eq
! nstemp   = 12     ! Nr. of temps
! temps    = 2.00 13.00 ! K  provide list of temperetures OR (nstemp and temps = tempsmin  tempsmax for even space mode)
nsiter   = 500
muc     = 0.20876
dvscf_dir   = '../../phonon/save'

nk1         = 12
nk2         = 12
nk3         = 1
nq1         = 6
nq2         = 6
nq3         = 1

!  mp_mesh_k = .true.
nkf1 = 60
nkf2 = 60
nkf3 = 1
nqf1 = 60
nqf2 = 60
nqf3 = 1
/
``````
The above are the input files for my two calculations. Thank you.

hlee
Posts: 332
Joined: Thu Aug 03, 2017 12:24 pm
Affiliation: The University of Texas at Austin

Re: Why is the density of states at Fermi level output by EPW inconsistent with that calculated by dos.x?

Dear dhw:
How do I do this interpolation? Use EPW interpolation?
You compared the DOS from nscf calculations on a 60x60x1 k grids with that from the energies "interpolated" on the same grid using EPW.
In this case, (as I said in my previous post) depending on the Wannier interpolation quality, two DOSs can be different.

Another point is that in your dos.x calculation, you used Simple Gaussian (default, ngauss=0), but in your EPW calculation, you used ngauss=1 (default in EPW, Methfessel-Paxton of order 1) for the evaluation of DOS.

Sincerely,

H. Lee