phDOS and a2F not matching

[simba2828]

Dear EPW Users and developer,

What can be the possible reason that my a2F and phDOS are not in good agreement?
I am attaching the figure showing the two quantities, kindly let me know what could be done to match them. I am using fine grids of k 120 120 1 and of q 120 120 1.

Sincerely,
Shubham

[hlee]

Dear simba2828:

Could you provide us with all relevant inputs and outputs?

Sincerely,

H. Lee

[simba2828]

Dear Lee,

The phonon scf and el-ph inputs are:
(Using Norm-conserving Pseudopotentials)

Code: Select all

&CONTROL
    calculation = "scf"
    verbosity='high'
    restart_mode = 'from_scratch',
    prefix       = 'nsms',
    pseudo_dir   = '../../pseudo/',
    outdir       = './out/'
/
&SYSTEM
    a                         =  3.31634e+00
    c                         =  3.19807e+01
    degauss                   =  0.02
    ecutwfc                   =  100
    ibrav                     = 4
    nat                       = 6
    ntyp                      = 4
    occupations               = "smearing"
    smearing                  = "gaussian"
/
&ELECTRONS
    conv_thr         =  1.00000d-10
    electron_maxstep = 200
    mixing_beta      =  0.7D0
    diagonalization='david'
    mixing_mode = 'plain'
/
ATOMIC_SPECIES
---
ATOMIC_POSITIONS {angstrom}
----
K_POINTS {automatic}
 12  12  1  0 0 0

el-ph input:

Code: Select all

&inputph
  tr2_ph=1.0d-14,
  prefix='nsms',
  fildvscf = 'dvscf',
  outdir='./out/',
  fildyn='nsms.dyn',
  electron_phonon='interpolated',
  el_ph_sigma=0.05,
  el_ph_nsigma=10,
  trans=.true.,
  ldisp=.true.,
  alpha_mix(1)=0.2,
  nq1=3, nq2=3, nq3=1
 /

The scf input for EPW is similar to phonon scf input and nscf input is just on an explicit grid.

EPW input:

Code: Select all

--
&inputepw
  prefix      = 'nsms',
  amass(1) = 92.90638,
  amass(2) = 78.96000,
  outdir      = './out/'

  ep_coupling = .true.
  elph        = .true.
  epbwrite    = .true.
  epbread     = .false.

  epwwrite = .true.
  epwread  = .false.

  !etf_mem     =  1 

  nbndsub     =  17,
  !nbndskip = 0
  bands_skipped = 'exclude_bands = 1:12,30,31'

  wannierize  = .false.
  num_iter    = 500
  dis_froz_max= 4.6
  dis_froz_min= -5.8


  wdata(1)   = 'dis_mix_ratio   = 0.5'
  wdata(2)   = 'dis_num_iter    = 2000'
  wdata(3)    = 'bands_plot : true'
  wdata(4)    = 'bands_num_points : 300'
  wdata(5)    = 'bands_plot_format : xmgrace gnuplot'
  wdata(6)    = 'begin kpoint_path'
  wdata(7)    = 'M 0.5 0.0 0.0 K 0.3333 0.3333 0.0'
  wdata(8)    = 'K 0.3333 0.3333 0.0 G 0.0 0.0 0.0'
  wdata(9)    = 'G 0.0 0.0 0.0 M 0.5 0.0 0.0'
  wdata(10)    = 'end kpoint_path'
  

  
  iverbosity  = 2

  eps_acustic = 0.1    ! Lowest boundary for the phonon frequency 
  ephwrite    = .true. ! Writes .ephmat files used when Eliasberg = .true.

  nsmear      = 1
  delta_smear = 0.01 ! eV 0.04

  degaussq     = 0.5 ! meV
  nqstep       = 500

  eliashberg  = .true.

  laniso = .true.
  limag = .true.
  lpade = .true.

  !lifc = .true.
  !band_plot=.true.  ! wannier-bands
  !efermi_read = .true.
  !fermi_energy = -1.779
  fermi_plot = .true.

  conv_thr_iaxis = 1.0d-3


  !nstemp   = 1     ! Nr. of temps
  !temps    = 15.00 ! K  provide list of temperetures OR (nstemp and temps = tempsmin  tempsmax for even space mode)

  temps(1)  = 30
  temps(2)  = 35
  temps(3)  = 40
  !temps(4) = 25


  nsiter   = 500
  degaussw    = 0.04 ! eV ~  1/4 of fsthick
  wscut = 0.4   ! eV 10 times of  Upper limit over frequency integration/summation in the Elisashberg eq(1 cm-1 ~ 1/8000 eV)
  fsthick     = 0.5  ! eV ~ 4 times the maximum phonon frequency 
  muc     = 0.1

  dvscf_dir   = '../ph/save'
  
  !system_2d = .true.

  nk1         = 12
  nk2         = 12
  nk3         = 1

  nq1         = 3
  nq2         = 3
  nq3         = 1

  mp_mesh_k = .true.
  nkf1 = 120
  nkf2 = 120
  nkf3 = 1

  nqf1 = 120
  nqf2 = 120
  nqf3 = 1
 /

The energy in scf successfully converged.

The EPW output:
Wannier spreads:

Code: Select all

 Running Wannier90

     Wannier Function centers (cartesian, alat) and spreads (ang):

     (   0.52860   0.30850   3.28954) :   2.91040
     (  -0.01941   0.52990   0.62406) :   3.29941
     (  -0.50699   0.28662   0.98432) :   1.95270
     (   0.53045   0.30403   0.98592) :   4.02847
     (   0.42110   0.33415   2.47315) :   2.92723
     (   0.05916   0.57557   1.43594) :   4.18362
     (  -0.49837   0.84791   2.88407) :   4.25075
     (  -0.48324   0.25313   2.46049) :   2.89389
     (   0.94054   0.58254   1.32918) :   3.09406
     (   0.46078   0.32498   3.31057) :   2.92685
     (   0.11614   0.59042   0.77775) :   8.90613
     (   0.01948   0.58563   0.52250) :   2.83155
     (   0.35754   0.79680   1.12665) :  17.07938
     (   0.07582   0.84352   0.83863) :   6.48211
     (   0.01722   0.57866   1.37885) :   3.03082
     (  -0.48638   0.24137   3.28777) :   2.89536
     (  -0.94327  -0.57897   2.49834) :   2.97238

     -------------------------------------------------------------------
     WANNIER      :     49.44s CPU     50.84s WALL (       1 calls)
     -------------------------------------------------------------------

     Calculating kgmap

     Progress kgmap: ########################################
     kmaps        :      0.73s CPU      1.82s WALL (       1 calls)

Code: Select all

   Progression iq (fine) =      14200/     14400
     Progression iq (fine) =      14300/     14400
     Progression iq (fine) =      14400/     14400
                  Fermi level (eV) =    0.667883489617196D+00
     DOS(states/spin/eV/Unit Cell) =    0.147168465827109D+01
            Electron smearing (eV) =    0.400000000000000D-01
                 Fermi window (eV) =    0.500000000000000D+00

     Finish writing .ephmat files

     ===================================================================
     Memory usage:  VmHWM =       834Mb
                   VmPeak =      4885Mb
     ===================================================================


     Finish writing dos file nsms.dos


     Finish writing phdos files nsms.phdos and nsms.phdos_proj

     Fermi surface calculation on fine mesh
                  Fermi level (eV) =   0.667883
           5   bands within the Fermi window


     ===================================================================
     Solve anisotropic Eliashberg equations
     ===================================================================


     Finish reading freq file

                  Fermi level (eV) =     6.6788348962E-01
     DOS(states/spin/eV/Unit Cell) =     1.4716846583E+00
            Electron smearing (eV) =     4.0000000000E-02
                 Fermi window (eV) =     5.0000000000E-01
     Nr irreducible k-points within the Fermi shell =      2405 out of      2461

           4 bands within the Fermi window


     Finish reading egnv file


     Max nr of q-points =     14064


    805,50        56%
     Max nr of q-points =     14064


     Finish reading ikmap files


     Size of allocated memory per pool: ~=    1.4949 Gb

     Start reading .ephmat files


     Finish reading .ephmat files

     a2f file is not found to estimate initial gap: calculating a2f files


     Finish reading a2f file

     Electron-phonon coupling strength =    1.8074196

     Estimated Allen-Dynes Tc =    19.995505 K for muc =    0.10000

     Estimated w_log in Allen-Dynes Tc =    12.891461 meV

     Estimated BCS superconducting gap =     3.032620 meV

     Estimated Tc from machine learning model =    25.660110 K


     WARNING WARNING WARNING

     The code may crash since tempsmax =   25.000 K is larger than Allen-Dynes Tc =    19.996 K

     temp(  1) =     17.00000 K

     Solve anisotropic Eliashberg equations on imaginary-axis

     Total number of frequency points nsiw(     1) =     43
     Cutoff frequency wscut =     0.4004


     Size of allocated memory per pool: ~=    1.4949 Gb

Size of allocated memory per pool: ~=    1.4949 Gb
     Actual number of frequency points (     1) =     43 for uniform sampling

     Size of allocated memory per pool: ~=    1.4958 Gb

     Size of allocated memory per pool: ~=    1.4990 Gb

     Size of required memory per pool: ~=    7.4106 Gb

     Size of allocated memory per pool: ~=    1.4990 Gb

     akeri is calculated on the fly since its size exceedes max_memlt

        iter      ethr          znormi      deltai [meV]
          1   3.161528E+00   2.680787E+00   3.456038E+00
          2   1.756678E-01   2.666673E+00   3.607143E+00
          3   1.173026E-01   2.651875E+00   3.754762E+00
          4   2.866368E-02   2.641934E+00   3.862371E+00
          5   1.505935E-02   2.635263E+00   3.939232E+00
          6   1.160137E-02   2.640763E+00   3.873171E+00
          7   2.144168E-02   2.633193E+00   3.974200E+00
          8   5.025427E-03   2.634561E+00   3.953667E+00
          9   2.052838E-04   2.634557E+00   3.953488E+00
         10   4.426619E-03   2.633305E+00   3.971049E+00
         11   1.256529E-03   2.633636E+00   3.965964E+00
         12   7.709848E-04   2.633358E+00   3.969196E+00
         13   8.094553E-04   2.633092E+00   3.972491E+00
         14   3.659890E-04   2.632953E+00   3.974060E+00
         15   8.515549E-04   2.632657E+00   3.977624E+00
         16   6.949045E-04   2.632412E+00   3.980559E+00
         17   1.317771E-03   2.631954E+00   3.986052E+00
         18   1.206770E-03   2.631541E+00   3.991034E+00
         19   8.875571E-04   2.631235E+00   3.994733E+00
         20   9.139661E-04   2.630917E+00   3.998560E+00
         21   3.658255E-04   2.630798E+00   4.000028E+00
         22   3.230211E-04   2.630702E+00   4.001283E+00
         23   7.318691E-04   2.630479E+00   4.004131E+00
         24   5.281245E-04   2.630319E+00   4.006173E+00
         25   5.399595E-04   2.630155E+00   4.008275E+00
         26   5.785427E-04   2.629987E+00   4.010482E+00
         27   5.883726E-04   2.629804E+00   4.012773E+00
         28   7.300649E-04   2.629589E+00   4.015570E+00
         29   6.870195E-04   2.629387E+00   4.018223E+00
         30   5.289478E-04   2.629237E+00   4.020230E+00
         31   2.823832E-04   2.629152E+00   4.021331E+00
         32   3.885391E-04   2.629041E+00   4.022816E+00
         33   3.338970E-04   2.628938E+00   4.024127E+00
         34   4.078674E-04   2.628814E+00   4.025719E+00
         35   3.793983E-04   2.628698E+00   4.027212E+00
	 36   3.286585E-04   2.628599E+00   4.028500E+00
         37   4.140730E-04   2.628461E+00   4.030178E+00
         38   4.815387E-04   2.628308E+00   4.032083E+00
         39   4.197186E-04   2.628173E+00   4.033746E+00
         40   2.600534E-04   2.628087E+00   4.034790E+00
         41   2.195260E-04   2.628016E+00   4.035666E+00
         42   2.623691E-04   2.627933E+00   4.036704E+00
         43   2.870899E-04   2.627842E+00   4.037839E+00
         44   3.161577E-04   2.627745E+00   4.039080E+00
         45   3.549629E-04   2.627633E+00   4.040472E+00
         46   2.703714E-04   2.627547E+00   4.041532E+00
         47   2.173038E-04   2.627479E+00   4.042376E+00
         48   2.499306E-04   2.627402E+00   4.043349E+00
         49   1.505975E-04   2.627356E+00   4.043930E+00
         50   1.829023E-04   2.627302E+00   4.044638E+00
         51   2.734025E-04   2.627223E+00   4.045677E+00
         52   2.004033E-04   2.627163E+00   4.046452E+00
         53   1.518634E-04   2.627120E+00   4.047034E+00
         54   2.671786E-04   2.627039E+00   4.048069E+00
         55   1.853435E-04   2.626980E+00   4.048805E+00
         56   1.851484E-04   2.626924E+00   4.049524E+00
         57   2.262582E-04   2.626855E+00   4.050405E+00
         58   9.514811E-05   2.626826E+00   4.050782E+00
     Convergence was reached in nsiter =     58

     Chemical potential (itemp =   1) =     6.6788348962E-01 eV

     Temp (itemp =   1) =   17.000 K  Free energy =    -0.005508 meV


     Size of allocated memory per pool: ~=    1.4990 Gb

     Size of allocated memory per pool: ~=    1.4981 Gb

     Size of allocated memory per pool: ~=    1.4950 Gb
     Min. / Max. values of superconducting gap =    -0.878615    4.432438 meV
     iaxis_imag   :   7608.56s CPU   7609.08s WALL (       1 calls)


     Pade approximant of anisotropic Eliashberg equations from imaginary-axis to real-axis
     Cutoff frequency wscut =     0.4000


     Size of allocated memory per pool: ~=    1.5123 Gb
        pade    Re[znorm]   Re[delta] [meV]
         38   2.827459E+00   3.890757E+00

     Convergence was reached for N =     38 Pade approximants


....

I checked various combinations of k/q grids, wscut,fsthick, degaussw, muc etc but still no improvement in the a2f and phdos. They are still distinct.
If any other details required kindly let me know.

One more thing, I am getting negative value of Min Superconduction gap. Kindly check the line in the input. Would you like to comment on that?

Code: Select all

   Min. / Max. values of superconducting gap =    -0.878615    4.432438 meV
     iaxis_imag   :   7608.56s CPU   7609.08s WALL (       1 calls)

Shubham

[simba2828]

Dear H Lee Sir,
Could you please comment on the query? I have performed many trial calculations for el-ph and EPW but the a2F and phDOS is not matching.

Shubham

[hpaudya1]

Hi Shubham,

I did not understand what you mean by "did not match". Phdos and a2f are two different quantities calculated using two different equations, and why should they match?

One thing I noticed is that your Wannier spreads are large for some of the projections, is that acceptable? Did you check the DFT bands on the top of the Wannier bands? And also can you confirm that the coarse mesh Fermi energy (scf.out/nscf.out) and fine mesh Fermi energy (epw.out) are close?

Happy EPWing,
Hari

[simba2828]

Dear Hari Sir,

1. I have seen many papers where authors explicitly mention that phDOS and spectral density function (a2F(w)) both match at some extent.

2. Yes, I checked Wannier bands are matching with the DFT bands. Slight difference can be seen very far from the Fermi level. Will that affect my calculations?
3. Yes, The Fermi energies match in both the cases: nscf/scf: 1.8972 eV , EPW Fermi energy: 1.857049 eV.

Shubham

[hpaudya1]

Hi Shubham,

Could you double check your phonon dispersion and the density of states both with QE and EPW? You can use https://docs.epw-code.org/doc/Inputs.html#band-plot flag to interpolate your band/phonon.

One more thing I noticed is that you have "amass(1) = 92.90638, amass(2) = 78.96000," in your epw input file, however I see "ntyp = 4" in the scf. Could you double check these? I think something is going wrong in your EPW calculation around this.

Happy EPWing,
Hari

[simba2828]

Dear Hari Sir,

Could you please tell me how I can generate filkf and filqf files which are needed for band_plot to get the phonon bands using EPW?

Thank you

[hpaudya1]

Hi Shubham,

Can you check the following post? viewtopic.php?t=1226

Happy EPWing,
Hari

[simba2828]

Yeah Thank you, I was trying the same, and there I had to delete all the brackets and non-arithmetic symbols and I am putting wk = *** as the weight of that k-point. Is that correct?