EPW Forum

Dear all,

I'm trying to find superconducting properties of PdCoO2 solving isotropic Eliashberg equations. I've been able to get correct band structure using wannierization and phonons with tag lifc=TRUE. But whenever I try to solve Eliashberg equations, I get very large values of Allen-dynes Tc, which leads to incorrect initial guess for gap. Please kindly suggest what could I possibly change or try in the following input
Below is my input & output for running epw

&inputepw
prefix = 'PdCoO2',
outdir = './'
dvscf_dir = '../../phonon_444/save'
iverbosity = 3

ep_coupling = .true.
elph = .true.
epwwrite = .true.
epwread = .false.
lifc = .true.
wannierize = .true.
nbndsub = 10
efermi_read = .true.
fermi_energy = 14.5352


num_iter = 1000
dis_froz_min= 12
dis_froz_max= 17
proj(1) = 'Pd:d'
proj(2) = 'Co:d'



degaussw = 0.2 ! eV
degaussq = 0.5 ! meV
fsthick = 5 ! eV

ephwrite = .true.
eliashberg = .true.

liso = .true.
limag = .true.
lpade = .true.
lacon = .true.

nsiter = 500
npade = 40
conv_thr_iaxis = 1.0d-3
conv_thr_racon = 1.0d-3

wscut = 0.8 ! eV
muc = 0.1
nstemp = 10
temps = 0.25 10.25

mp_mesh_k = .true.
nkf1 = 24
nkf2 = 24
nkf3 = 24
nqf1 = 24
nqf2 = 24
nqf3 = 24
nk1 = 8
nk2 = 8
nk3 = 8
nq1 = 4
nq2 = 4
nq3 = 4
/
------------------------------------------------------------------------

Output is attached.
Thanks!!

Best regards,
Prachi.

Hi Prachi,

I noticed;

"Electron-phonon coupling strength = 0.0845567"

which is very small, and Tc is zero

Best,
Hari

Hi Hari,

Thanks for your reply. Yes, the coupling constant is very small.
I've a small question, the output files have '*******' in place of Tc. Does this mean its zero?
Because if I plug the numbers for coupling constant and w_log in the output file to find Tc, I got a very large number.

Thanks again.
Best regards,
Prachi.

Hi Prachi,

The Tc is printed as follows
https://gitlab.com/QEF/q-e/-/blob/devel ... d.f90#L729

******* in your output file does not mean zero, but the way it is printed is not appropriate to print the very small value which is close to zero.

Best,
Hari

Hi Hari,

I see. Thanks a lot for the explanation.

Best regards,
Prachi.