EPW Forum

Hi Shubham, When conducting DFT calculations, the fundamental premise, in my opinion, is to model electronic systems at absolute zero temperature since DFT is primarily a formalism for describing the ground state. If you adhere to this principle, smearing should be regarded as a parameter associated...

Hi Shubham, Except for the last question, I will answer the questions quickly as they are less relevant to EPW. Q: Why the instability disappears with large smearing value? Is there a direct relation between CDW and smearing? A: To account for instability stemming from CDW in calculations, reproduci...

Dear Paritosh,

In the current implementation (version 5.8), there is no way to avoid recalculating ephmat files.
You should recalculate them every time you change degaussw or fsthick.

Best regards,
Hitoshi

Dear Jianguo, What I am mentioning is the initial guess of the gap function Δ(iω, T). The first temperature should be specified by you in the input file. In BCS theory, in the weak-coupling limit, it is known that Δ(T-->0)=Δ_0=1.76 * kTc. Using this relation, the EPW estimates the gap function at ze...

Hi Jianguo, Perhaps, it seems that the number of the Matsubara frequencies may be insufficient with respect to temperature. In that case, it's understandable that the numerical solution becomes unstable. You should try with higher wscut. Additionally, you should know how to determine the initial val...

Hi Jianguo, Unfortunately, I am unable to view the attached image, so I can only provide general comments. To achieve converged results, it is necessary to test wscut and the sizes of the k and q grids (nkf1, nkf2, nkf3, nqf1, nqf2, and nqf3). It is advisable to set wscut to at least 5 times the max...

Hi,

It appears that the Wannier bands fail to accurately reproduce the DFT bands, as evidenced by the discrepancy in the Fermi energy calculated with Wannier bands compared to that of DFT. Have you investigated the variance between them?

Best,
Hitoshi

Hello Henry, In the nscf calculation just before running epw, you should use a homogeneous grid of nk1 x nk2 x nk3. Note that you cannot automatically specify the k points as in the scf calculation, which means you do not use "K_POINTS automatic". We strongly suggest using "kmesh.pl", that is the sc...

Dear Xiaming, There's a knack for correctly outputting a frmsf file from the superconducting module. The previous versions (<= v.5.7) replace eigenvalues outside the fsthick window by a dummy value. That's why you sometimes get fake Fermi surfaces. To avoid this problem, you may increase the fsthick...

Hi Jianguo, I suppose you are working on the anisotropic Eliashberg calculation. Please check the following points: (1) Did you use mp_mesh_k? If not, please use "mp_mesh_k = .true." (2) Which value of iverbosity did you set? You do not need to set "iverbosity = 2" to solve the ME equations, "iverbo...