EPW Forum

Posted: **Wed Jun 15, 2016 5:36 am**

Dear all,

I am Seungjun Lee, I am interested in electron imaginary self energy (electron relaxation time)

I am using EPW 4.0.0 version and lastest version QE.
I want to calculate optical and acoustic phonon mode contribution of electron imaginary self energy.

So, I try some test using eps_acustic option.
(I understand that eps_acustic option set lower boundary of phonon frequency of input data, Is it right?)

I try to tested 2 cases, silicone and phosphorene.

First, I run EPW without eps_acustic option, (defalut : 5 cm-1) - (1)
next, I run EPW with eps_acustic option each cases. - (2)

and then, I calculate optical mode contribution using (2) / (1)

From my result, silicone cases, optical mode has 50% contribution of electron imaginary self energy. (set eps_acustic : 400 cm-1)
phosphorene cases, optical mode has 90% contribution of electron imaginary self energy. (set eps_acustic : 200 cm-1, This result is similar to PHYSICAL REVIEW B 91, 235419 (2015) )

Then, I have two questions about eps_acustic.

First, This method is right?
If my method was right, my results are some strange.

In non-polar materials, acoustic phonon mode is dominated in electron - phonon scattering.
So, I cannot understand my result.

How can I understand this result?

attached my input file
thank you.

Best Regards,
Seungjun Lee

Code: Select all

--
&inputepw
  prefix      = 'Si'
  amass(1)    = 28.0885
  outdir      = './'

  iverbosity  = 0

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

  epwwrite    = .true.
  epwread     = .false.

  nbndsub     =  8
  nbndskip    =  0

  wannierize  = .true.
  num_iter    = 1000
  iprint      = 2
  dis_win_max = 17
  dis_froz_max= 6
  proj(1)     = 'Si:sp3'   

  elinterp    = .true.
  phinterp    = .true.

  tshuffle2   = .true.
  tphases     = .false.

  elecselfen  = .ture.
  phonselfen  = .false.
  a2f         = .false.

  parallel_k  = .true.
  parallel_q  = .false.

  fsthick     = 15 ! eV 
  eptemp      = 300 ! K (same as PRB 76, 165108)
  degaussw    = 1.0 ! eV

  eps_acustic = 400

  dvscf_dir   = './save'
  filukk      = './Si.ukk'
  filkf       = './mesh.dat'

!  nkf1        = 20
!  nkf2        = 20
!  nkf3        = 20

  nqf1        = 50
  nqf2        = 50
  nqf3        = 50
  
  nk1         = 6
  nk2         = 6
  nk3         = 6

  nq1         = 6
  nq2         = 6
  nq3         = 6
 /
      16 cartesian
   0.0000000   0.0000000   0.0000000  0.0092593
  -0.1666667   0.1666667  -0.1666667  0.0740741
  -0.3333333   0.3333333  -0.3333333  0.0740741
   0.5000000  -0.5000000   0.5000000  0.0370370
   0.0000000   0.3333333   0.0000000  0.0555556
  -0.1666667   0.5000000  -0.1666667  0.2222222
   0.6666667  -0.3333333   0.6666667  0.2222222
   0.5000000  -0.1666667   0.5000000  0.2222222
   0.3333333   0.0000000   0.3333333  0.1111111
   0.0000000   0.6666667   0.0000000  0.0555556
   0.8333333  -0.1666667   0.8333333  0.2222222
   0.6666667   0.0000000   0.6666667  0.1111111
   0.0000000  -1.0000000   0.0000000  0.0277778
   0.6666667  -0.3333333   1.0000000  0.2222222
   0.5000000  -0.1666667   0.8333333  0.2222222
  -0.3333333  -1.0000000   0.0000000  0.1111111

Code: Select all

--
&inputepw
  prefix      = 'P'
  amass(1)    = 30.9738
  outdir      = './'

  iverbosity  = 0

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

  epwwrite    = .true.
  epwread     = .false.

  nbndsub     =  16
  nbndskip    =  0

  wannierize  = .true.
  num_iter    = 2000
  iprint      = 2
!  dis_win_max = 12
!  dis_froz_max= 7
  proj(1)     = 'P:sp3'   
  wdata(1)    = 'dis_num_iter = 2000'
  wdata(2)    = 'guiding_centres = ture'

  elinterp    = .true.
  phinterp    = .true.

  tshuffle2   = .true.

  tphases     = .false.

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

  eps_acustic = 200

  parallel_k  = .true.
  parallel_q  = .false.

  fsthick     = 20 ! eV 
  eptemp      = 300 ! K (same as PRB 76, 165108)
  degaussw    = 0.01 ! eV

  dvscf_dir   = './save/'
  filukk      = './P.ukk'
  filkf       = './mesh.dat'

  nqf1        = 50
  nqf2        = 50
  nqf3        = 1
  
  nk1         = 10
  nk2         = 10
  nk3         = 1

  nq1         = 10
  nq2         = 10
  nq3         = 1
 /
      36 cartesian
           0.0000000   0.0000000   0.0000000   0.0200000
           0.0000000   0.1404281   0.0000000   0.0400000
           0.0000000   0.2808562   0.0000000   0.0400000
           0.0000000   0.4212842   0.0000000   0.0400000
           0.0000000   0.5617123   0.0000000   0.0400000
           0.0000000  -0.7021404   0.0000000   0.0200000
           0.1000000   0.0000000   0.0000000   0.0400000
           0.1000000   0.1404281   0.0000000   0.0800000
           0.1000000   0.2808562   0.0000000   0.0800000
           0.1000000   0.4212842   0.0000000   0.0800000
           0.1000000   0.5617123   0.0000000   0.0800000
           0.1000000  -0.7021404   0.0000000   0.0400000
           0.2000000   0.0000000   0.0000000   0.0400000
           0.2000000   0.1404281   0.0000000   0.0800000
           0.2000000   0.2808562   0.0000000   0.0800000
           0.2000000   0.4212842   0.0000000   0.0800000
           0.2000000   0.5617123   0.0000000   0.0800000
           0.2000000  -0.7021404   0.0000000   0.0400000
           0.3000000   0.0000000   0.0000000   0.0400000
           0.3000000   0.1404281   0.0000000   0.0800000
           0.3000000   0.2808562   0.0000000   0.0800000
           0.3000000   0.4212842   0.0000000   0.0800000
           0.3000000   0.5617123   0.0000000   0.0800000
           0.3000000  -0.7021404   0.0000000   0.0400000
           0.4000000   0.0000000   0.0000000   0.0400000
           0.4000000   0.1404281   0.0000000   0.0800000
           0.4000000   0.2808562   0.0000000   0.0800000
           0.4000000   0.4212842   0.0000000   0.0800000
           0.4000000   0.5617123   0.0000000   0.0800000
           0.4000000  -0.7021404   0.0000000   0.0400000
          -0.5000000   0.0000000   0.0000000   0.0200000
          -0.5000000   0.1404281   0.0000000   0.0400000
          -0.5000000   0.2808562   0.0000000   0.0400000
          -0.5000000   0.4212842   0.0000000   0.0400000
          -0.5000000   0.5617123   0.0000000   0.0400000
          -0.5000000  -0.7021404   0.0000000   0.0200000

Posted: **Wed Jun 15, 2016 9:22 am**

Hi Seungjun,

The variable eps_acustic is only meant to discard the 3 translational modes at Gamma, and it is set by default to 5 cm^-1.

This variable is not meant in any way to test the contribution of acoustic phonons to self-energies and other physical properties, its only purpose is to avoid including contributions which would be identically zero in an exact theory.

FG

Posted: **Wed Jun 15, 2016 1:49 pm**

Dear giustino,

Thank you for your kind reply.

Best regards,
Seungjun Lee

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