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How to select degaussw ? 
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Joined: Thu Nov 29, 2018 9:02 am
Posts: 22
University: Institute of Physics
Post How to select degaussw ?
Dear all,

I am trying to calculate the electron-phonon coupling in TiSe_2 and I got the following result.
Image
Then I'm confused about how to select correct the smearing parameter of delta function which is controlled by the tag degaussw.
I found two similar graph in the literature https://journals.aps.org/prb/abstract/10.1103/PhysRevB.95.024505
Image
Image
I have review some discussion about this parameter, I thought that if we increase k-mesh or q-mesh, the lambda will converge to an constant.
But in my case and the PRB case, the lambda just increase when sigma close to 0 even when we increase k&q mesh.
Why we can select 15meV or 35meV as the convergence criterion value?
Hope for any discussion about this.

Bests,
Xinbao,


Sun Jun 02, 2019 2:46 pm
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Joined: Mon Dec 17, 2018 12:43 pm
Posts: 22
University: Faculty of sc 'rbt'
Post Re: How to select degaussw ?
HI
i have the same problem for the electron phonon coupling for an 2D metal
i got unreasonable electron phonon coupling and eliashberg spectral function for a q and k meshes 320*200*1 and 320*200*1
i had lambda = 290
Code:
&inputepw
  prefix      = 'xx'
  amass(1)    = xxxxxxxxxx
  outdir      = './'

  iverbosity  = 1
!ep_coupling = .false.
  elph        = .true.
  kmaps       = .false.
  epbwrite    = .true.
  epbread     = .false.

!  etf_mem     = 0

  epwwrite    = .true.
  epwread     = .false.

  nbndsub     =  8
  nbndskip    =  0

  wannierize  = .true.
  num_iter    = 150
  iprint      = 2
  dis_win_max = 20
  dis_froz_max= -1
  proj(1)     = 'xx:l=-3'   

  elecselfen  = .false.
! nest_fn     = .false. 
  phonselfen  = .true.
  a2f         = .true.
  delta_approx = .true.

! specfun_el   = .true.
  wmin_specfun = 0
  wmax_specfun = 0.001
  nw_specfun   = 50

! parallel_k  = .true.
!  parallel_q  = .false.

!wdata(9) = 'kmesh_tol=0.00001'
  wdata(1) = 'bands_plot = .true.'
  wdata(2) = 'begin kpoint_path'
  wdata(3) = 'G 0.00 0.00 0.00 X 0.50 0.00 0.00'
  wdata(4) = 'X 0.50 0.00 0.00 S 0.50 0.50 0.00'
  wdata(5) = 'S 0.50 0.50 0.00 Y 0.00 0.50 0.00'
  wdata(6) = 'Y 0.00 0.50 0.00 G 0.00 0.00 0.00'
  wdata(7) = 'end kpoint_path'
  wdata(8) = 'bands_plot_format = gnuplot'
  wdata(9) = 'search_shells=40'
  wdata(10) = 'dis_num_iter= 20000'

  fsthick     = 15 ! eV
  eptemp      = 0.075 ! K (same as PRB 76, 165108)
  degaussw    = 0.025 ! eV
  degaussq    = 0.5 ! meV
  dvscf_dir   = '../phonon/save/'
  filukk      = './xx.ukk'
!  filkf       = 'xx_band.kpt'
! filqf = 'kpath.dat'




nkf1        = 320
nkf2        = 200
nkf3        = 1

  nqf1        = 320
  nqf2        = 200
  nqf3        = 1
 
  nk1         = 32
  nk2         = 20
  nk3         = 1

  nq1         = 16
  nq2         = 10
  nq3         = 1
/
      54 cartesian
     0.000000000   0.000000000   0.000000000
     0.000000000   0.098901334   0.000000000
     0.000000000   0.197802667   0.000000000
     0.000000000   0.296704001   0.000000000
     0.000000000   0.395605335   0.000000000
     0.000000000  -0.494506669   0.000000000
     0.062500000   0.000000000   0.000000000
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     0.250000000  -0.494506669   0.000000000
     0.312500000   0.000000000   0.000000000
     0.312500000   0.098901334   0.000000000
     0.312500000   0.197802667   0.000000000
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     0.312500000  -0.494506669   0.000000000
     0.375000000   0.000000000   0.000000000
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     0.375000000   0.197802667   0.000000000
     0.375000000   0.296704001   0.000000000
     0.375000000   0.395605335   0.000000000
     0.375000000  -0.494506669   0.000000000
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     0.437500000   0.098901334   0.000000000
     0.437500000   0.197802667   0.000000000
     0.437500000   0.296704001   0.000000000
     0.437500000   0.395605335   0.000000000
     0.437500000  -0.494506669   0.000000000
    -0.500000000   0.000000000   0.000000000
    -0.500000000   0.098901334   0.000000000
    -0.500000000   0.197802667   0.000000000
    -0.500000000   0.296704001   0.000000000
    -0.500000000   0.395605335   0.000000000
    -0.500000000  -0.494506669   0.000000000


Mon Jun 10, 2019 12:13 pm
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