Different values of lambda and Tc (iso vs aniso?)

Dear all,

I am calculating lambda using two different methods implemented in EPW.

First one is obtained by activating anisotropic Eliashberg equation related tags.

**Code:**

eliashberg = .true.

laniso = .true.

limag = .true.

lpade = .true.

The result is as below:

**Code:**

===================================================================

Solve anisotropic Eliashberg equations

===================================================================

Finish reading .freq file

Fermi level (eV) = 1.4490810867E+00

DOS(states/spin/eV/Unit Cell) = 7.4601791612E-01

Electron smearing (eV) = 1.0000000000E-01

Fermi window (eV) = 4.0000000000E-01

Nr irreducible k-points within the Fermi shell = 134 out of 231

2 bands within the Fermi window

Finish reading .egnv file

Max nr of q-points = 466

Finish reading .ikmap files

Start reading .ephmat files

Finish reading .ephmat files

lambda_max = 1.3814131 lambda_k_max = 0.7463819

Electron-phonon coupling strength = 0.5890385

Estimated Allen-Dynes Tc = 1.0488626 K for muc = 0.16000

Estimated BCS superconducting gap = 0.0001591 eV

and the second one is obtained by activating a2f tags and deactivating anisotropic Eliashberg tags.

**Code:**

a2f = .true.

phonselfen = .true.

The result is as below:

**Code:**

===================================================================

Eliashberg Spectral Function in the Migdal Approximation

===================================================================

lambda : 0.5689812

lambda_tr : 0.7333977

Estimated Allen-Dynes Tc

logavg = 0.0006900 l_a2F = 0.5735213

mu = 0.10 Tc = 2.164145346702 K

mu = 0.12 Tc = 1.691229225724 K

mu = 0.14 Tc = 1.276401502717 K

mu = 0.16 Tc = 0.922975116778 K

mu = 0.18 Tc = 0.632737937327 K

mu = 0.20 Tc = 0.405375457882 K

The lambda obtained by the first one is 0.5890385, while the lambda from the second method is 0.5689812. and T_c is also slightly different.

Could it be understood it is because of the effect of anisotropic nature of the system? or some bugs in the code or numerical inaccuracy? I've calculated the second part by re-loading previously obtained files that required solving the Eliashberg equation. Any comments would be helpful and appreciate.

Best regards,

Jun-Ho