[Pw_forum] Zero scattering rates for bulk Ge for some k points using EPW

[Vahid Askarpour]

Dear QE Users,

I am not sure if this possible bug is QE related or EPW related so let me try reporting it here. I have installed espresso-5.4.0 and EPW-5.4.0 in my $HOME on a Linux cluster using intel-14.0.2 and openmpi-1.6.5. To calculate the electron-phonon scattering rates for a 2-atom germanium unit cell, I chose a 6x6x6 k and q coarse grids and 20x20x20 and 40x40x40 fine grids for electrons and phonons, respectively using Ge.pz-hgh.UPF PSP. My EPW input file is given below. I generate 8 Wannier functions (4 valence+4 conduction) using sp3 projection. The scattering rates agree with Rideau results (DOI:10.1109/SISPAD.2011.6035046). However, some of the scattering rates are zero at certain k points and I think they shouldn’t be zero.  I would appreciate any thoughts you may have on these zero rates. I tried attaching the scattering rates but the size (900k) was over the limit allowed by the QE forum.

Thank you,

Vahid

Vahid Askarpour
Department of Physics and Atmospheric Science
Dalhousie University
Halifax, NS, Canada

--
&inputepw
 prefix      = 'ge'
 amass(1)    = 72.63
 outdir      = './'

 iverbosity  = 0

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

 epwwrite    =  .true.
 epwread     =  .false.

 nbndsub     =  8
 nbndskip    =  0

 wannierize  = .true.
 num_iter    = 300
 iprint      = 2
 dis_win_max = 17
 dis_froz_max= 6
 proj(1)     = 'Ge:sp3'   

 elinterp    = .true.
 phinterp    = .true.

 tshuffle2   = .true.
 tphases     = .false.

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

 parallel_k  = .true.
 parallel_q  = .false.

 fsthick     = 2 ! eV 
 eptemp      = 300 ! K
 degaussw    = 0.03 ! eV

 dvscf_dir   = '../phonons/save'
 filukk      = './ge.ukk

 nkf1        = 20
 nkf2        = 20
 nkf3        = 20

 nqf1        = 40
 nqf2        = 40
 nqf3        = 40

 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