Matrix elements of Si with EPW

[gbrunin]

Hello,

For tests purposes, I am trying to represent the matrix elements in the case of silicon, for q = Gamma and along a high-symmetry k-path as well as for k = Gamma and along a high-symmetry q-path. I represent g_{44,6} where the first indices correspond to the two electronic states (ibnd, jbnd), and 6 corresponds to the phonon mode (imode). The result is represented here :

https://paper.dropbox.com/doc/Matrix-el ... e_copylink

I obtained the DFPT results by running EPW on the initial coarse k grid, and the interpolation results from the same computation with a much denser grid. You can find my input file below. The results are quite weird... Would you have an idea where the shifts we see come from ? I have seen in the documentation that the degeneracy iband, jband and kmode is already done. Is there something else to do in this case ?

Thanks for your help,

Guillaume

Code: Select all

EPW computation for Si
&inputepw
  prefix      = 'Si'
  dvscf_dir   = '../ph/save/'
  amass(1)    = 28.086
  outdir      = './'

  elph        = .true.
  kmaps       = .true.

  epbread     = .true.
  epbwrite    = .false.

  epwwrite    = .true.
  epwread     = .false.

  etf_mem     = 1

  nbndsub     =  8
  nbndskip    =  0

  !wannierize  = .true.
  wannierize  = .false.
  num_iter    = 3000
  iprint      = 2
  dis_win_max  = 17
  dis_froz_max = 6.5
  proj(1)     = 'Si:sp3'

  wdata(1) = 'bands_plot = .true.'
  wdata(2) = 'begin kpoint_path'
  wdata(3) = 'G 0.000 0.000 0.000 X 0.000 0.500 0.500'
  wdata(4) = 'X 0.000 0.500 0.500 W 0.250 0.500 0.750'
  wdata(5) = 'W 0.250 0.500 0.750 K 0.375 0.375 0.750'
  wdata(6) = 'K 0.375 0.375 0.750 G 0.000 0.000 0.000'
  wdata(7) = 'G 0.000 0.000 0.000 L 0.500 0.500 0.500'
  wdata(8) = 'L 0.500 0.500 0.500 U 0.250 0.625 0.625'
  wdata(9) = 'U 0.250 0.625 0.625 W 0.250 0.500 0.750'
  wdata(10) = 'W 0.25 0.500 0.750 L 0.500 0.500 0.500'
  wdata(11) = 'L 0.50 0.500 0.500 K 0.375 0.375 0.750'
  wdata(12) = 'U 0.25 0.626 0.625 X 0.000 0.500 0.500'
  wdata(13) = 'end kpoint_path'
  wdata(14) = 'bands_plot_format = gnuplot'

  iverbosity  = 0

  elecselfen  = .true.
  phonselfen  = .true.
  a2f         = .true.

  prtgkk      = .true.

  parallel_k  = .true.
  parallel_q  = .false.

  fsthick     = 30  ! eV
  eptemp      = 1  ! K
  degaussw    = 0.01 ! eV
  degaussq    = 0.05 ! meV

  filukk      = './Si.ukk'

  efermi_read  = .true.
  fermi_energy = 6.241439

  nkf1        = 12
  nkf2        = 12
  nkf3        = 12

  filqf       = './qpt_path.dat'

  nk1         = 12
  nk2         = 12
  nk3         = 12

  nq1         = 6
  nq2         = 6
  nq3         = 6
 /
      16 cartesian
  0.000000000   0.000000000   0.000000000    0.004629629629629629
 -0.166666667   0.166666667  -0.166666667    0.037037037037037035
 -0.333333333   0.333333333  -0.333333333    0.037037037037037035
  0.500000000  -0.500000000   0.500000000    0.018518518518518517
  0.000000000   0.333333333   0.000000000    0.027777777777777776
 -0.166666667   0.500000000  -0.166666667    0.111111111111111111
  0.666666667  -0.333333333   0.666666667    0.111111111111111111
  0.500000000  -0.166666667   0.500000000    0.111111111111111111
  0.333333333   0.000000000   0.333333333    0.055555555555555556
  0.000000000   0.666666667   0.000000000    0.027777777777777776
  0.833333333  -0.166666667   0.833333333    0.111111111111111111
  0.666666667  -0.000000000   0.666666667    0.055555555555555556
  0.000000000  -1.000000000   0.000000000    0.013888888888888888
  0.666666667  -0.333333333   1.000000000    0.111111111111111111
  0.500000000  -0.166666667   0.833333333    0.111111111111111111
 -0.333333333  -1.000000000   0.000000000    0.055555555555555556

[sponce]

Hello Guillaume,

Looks like wrong Wannier functions.

Could you add plots in you Dropbox folder showing the following:
1) Plot the eigenenergies along L-G-X high symm. k-point path using the pw.x (nscf calculation)
On top of that plot, plot the interpolated results from EPW (that you get from using band_plot = .true.).
Make sure the results are the same

2) Exactly the same but for the phonons (use matdyn and EPW with band_plot that will produce an phband.freq file).

3) Make sure all the decay files decays properly

PS: If you really want to compare with DFPT, you need to hack the PHonon/PH/elphon.f90 code and run from there (more complicated).

Best,
Samuel