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Unit of logarithmic average of phonon frequencies

Posted: Mon Apr 10, 2017 6:03 am
by jhlee
Dear EPW users,

I am interested in electron-phonon interaction in two dimensional materials to understand collective phenomena.
Especially, I want to know the unit of logarithmic average of phonon frequencies in the output of epw, v.4.0.0.
In the output file, logavg = 0.0003401 can be found without unit.
The following are the details of my input and output files.

Code: Select all

epw
&inputepw
  prefix      = 'mote2'
  amass(1)    = 95.96
  amass(2)    = 127.6
  outdir      = './'
  time_max    = 170000

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

  epwwrite = .true.
  epwread  = .false.

  etf_mem     = .true.

  a2f =.true.
  phonselfen = .true.

  wannierize  = .true.
  num_iter    = 800
  dis_froz_max=  2.5
  dis_froz_min= -6.5
  dis_win_max=  4.5
  dis_win_min= -6.5
  proj(1)     = 'Mo:d'
  proj(2)     = 'Te:p'

  wdata(1) = 'bands_plot = .true.'
  wdata(2) = 'begin kpoint_path'
  wdata(3) = 'G 0.00 0.00 0.00 Y 0.00 0.50 0.00'
  wdata(4) = 'Y 0.00 0.50 0.00 M 0.50 0.50 0.00'
  wdata(5) = 'M 0.50 0.50 0.00 X 0.50 0.00 0.00'
  wdata(6) = 'X 0.50 0.00 0.00 G 0.00 0.00 0.00'
  wdata(7) = 'G 0.00 0.00 0.00 M 0.50 0.00 0.00'
  wdata(8) = 'end kpoint_path'
  wdata(9) = 'bands_plot_format = gnuplot'
  wdata(10) = 'guiding_centres = true'

  iverbosity  = 1

  parallel_k  = .true.
  parallel_q  = .false.

  eps_acustic = 2.0   
  ephwrite    = .true.

  fsthick     = 0.4  ! eV
  eptemp      = 300  ! K
  degaussw    = 0.10 ! eV
  nsmear      = 1
  delta_smear = 0.04 ! eV

  degaussq     = 0.5 ! meV
  nqstep       = 500

  eliashberg  = .true.

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

  conv_thr_iaxis = 1.0d-4

  wscut = 1.0   ! eV   

  nstemp   = 3
  tempsmin = 2.00
  tempsmax = 8.00

  nsiter   = 500

  muc     = 0.16

  dvscf_dir   = '../save'

  nk1         = 4
  nk2         = 8
  nk3         = 1

  nq1         = 4
  nq2         = 8
  nq3         = 1

  nkf1 = 20
  nkf2 = 40
  nkf3 = 1

  nqf1 = 20
  nqf2 = 40
  nqf3 = 1
 /
15 cartesian
0.000000000 0.000000000 0.000000000     0.01
0.000000000 0.227099715 0.000000000     0.02
0.000000000 0.454199430 0.000000000     0.01
0.000000000 0.681299145 0.000000000     0.02
0.000000000 -0.908398861 0.000000000    0.04
0.250000000 0.000000000 0.000000000     0.02
0.250000000 0.227099715 0.000000000     0.02
0.250000000 0.454199430 0.000000000     0.04
0.250000000 0.681299145 0.000000000     0.02
0.250000000 -0.908398861 0.000000000    0.02
-0.500000000 0.000000000 0.000000000    0.04
-0.500000000 0.227099715 0.000000000    0.02
-0.500000000 0.454199430 0.000000000    0.01
-0.500000000 0.681299145 0.000000000    0.02
-0.500000000 -0.908398861 0.000000000   0.01


output is below.

Code: Select all

.
.
     ===================================================================
     Eliashberg Spectral Function in the Migdal Approximation
     ===================================================================

     lambda :    2.9539627
     lambda_tr :    2.5730481

     Estimated Allen-Dynes Tc

     logavg =    0.0003401 l_a2F =    2.9830315
     mu =   0.10 Tc =         9.639527937051 K
     mu =   0.12 Tc =         9.325415447053 K
     mu =   0.14 Tc =         9.008365664317 K
     mu =   0.16 Tc =         8.688529631271 K
     mu =   0.18 Tc =         8.366082310892 K
     mu =   0.20 Tc =         8.041225121179 K
     a2F          :      3.52s CPU      3.53s WALL (       1 calls)

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


     Finish reading .freq file

                  Fermi level (eV) =     1.3528688042E+00
     DOS(states/spin/eV/Unit Cell) =     1.0916033215E+00
            Electron smearing (eV) =     1.0000000000E-01
                 Fermi window (eV) =     4.0000000000E-01
     Nr k-points within the Fermi shell =       518 out of       800
           2 bands within the Fermi window
.
.
.


Thank you very much for your time.

Best,
Jun-Ho

Re: Unit of logarithmic average of phonon frequencies

Posted: Mon Apr 10, 2017 2:42 pm
by roxana
Dear Jun-Hu,

Looking in the code the logarithmic average of phonon frequencies is printed in file a2f.f90 (line 178) in the unit of the frequency which is Ryd. If you want to convert it to meV you can change line 178 to

WRITE(stdout,'(5x,a,f12.7,a,f12.7)') "logavg = ", logavg(1)*ryd2mev, " l_a2F = ", l_a2F(1)

and recompile the code.

Best,
Roxana

Re: Unit of logarithmic average of phonon frequencies

Posted: Mon Apr 10, 2017 10:50 pm
by jhlee
Dear Roxana,

Thank you very much!

Best,
Jun-Ho