A question about eps_acustic option.

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:2rxzh1ac]–
&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:2rxzh1ac]

[code:2rxzh1ac]–
&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[/code:2rxzh1ac]

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

Dear giustino,

Thank you for your kind reply.

Best regards,
Seungjun Lee