Dear Samuel Sir,

I am from IIT Ropar, a research institute in India. I am currently working on superconductivity in 2d materials like TMDCs etc.

Actually, for my research work, I need to do an EPW calculation. For this purpose, I saw your tutorial that is available on epw.org.uk, It is outstanding but when I do it on our PC it does not working in the "epw.out" file it shows calculating kgmap and do so for many days.

Please suggest to me, what I do for this type of calculation.

& What is the expected time taken to complete the task?

Thanks & Regards

Sahil Dani

## Need a help regarding EPW calculation!!

**Moderator:** hlee

### Re: Need a help regarding EPW calculation!!

Dear Sahil Dani:

Could you let me know which version of EPW you are using and provide me with your inputs (nscf.in and epw.in) and outputs (nscf.out and epw.out)?

Lastly, regarding the use of EPW for 2D materials, please check the page at viewtopic.php?f=3&t=1311 .

Sincerely,

H. Lee

Could you let me know which version of EPW you are using and provide me with your inputs (nscf.in and epw.in) and outputs (nscf.out and epw.out)?

Lastly, regarding the use of EPW for 2D materials, please check the page at viewtopic.php?f=3&t=1311 .

Sincerely,

H. Lee

### Re: Need a help regarding EPW calculation!!

Thanks for the reply,

Successfully got the results. But stuck in one problem

Regarding the surface plot using the python script "fermi_surf.py"

I have got a error ""print len(fermi_regex.findall(f))" How I resolve this error.

I am using the latest quantum espresso version.

Please if possible the latest python script so that this problem would be resolved.

With Regards

Sahil Dani

Successfully got the results. But stuck in one problem

Regarding the surface plot using the python script "fermi_surf.py"

I have got a error ""print len(fermi_regex.findall(f))" How I resolve this error.

I am using the latest quantum espresso version.

Please if possible the latest python script so that this problem would be resolved.

With Regards

Sahil Dani

### Re: Need a help regarding EPW calculation!!

Dear sahildani:

I don't know which script you are referring to, but please try python version 2 or modify this line so that it can be compatible with python 3.

Sincerely,

H. Lee

I don't know which script you are referring to, but please try python version 2 or modify this line so that it can be compatible with python 3.

Sincerely,

H. Lee

### Re: Need a help regarding EPW calculation!!

Hi sahildani:

If you want to plot Fermi surface, you can directly do it from the EPW now, which is newly implemented. For this, you can restart your calculation (if the first part is already done, you need .epmatwp, .ukk, .fmt, .kmap, .kgmap) with a flag 'fermi_plot = .true.'. This is done in band_plot level, and eigenvalues are interpolated for given nkf (set nqf = 1 for efficient calculation, if you are only calculating Fermi surface). You will get .cube files, which can be plotted with VESTA.

At some point, we are updating this in our website as soon as possible.

Best,

Hari

If you want to plot Fermi surface, you can directly do it from the EPW now, which is newly implemented. For this, you can restart your calculation (if the first part is already done, you need .epmatwp, .ukk, .fmt, .kmap, .kgmap) with a flag 'fermi_plot = .true.'. This is done in band_plot level, and eigenvalues are interpolated for given nkf (set nqf = 1 for efficient calculation, if you are only calculating Fermi surface). You will get .cube files, which can be plotted with VESTA.

At some point, we are updating this in our website as soon as possible.

Best,

Hari

### Re: Need a help regarding EPW calculation!!

Dear hpaudya1

Thanks for your kind reply, It's really helpful for me.

Can you suggest how to calculate the epw calculation for the 2d materials? Like 2D TMDs etc.

Thanks with Regards

Sahil Dani

Thanks for your kind reply, It's really helpful for me.

Can you suggest how to calculate the epw calculation for the 2d materials? Like 2D TMDs etc.

Thanks with Regards

Sahil Dani

### Re: Need a help regarding EPW calculation!!

Dear hlee SIr

I am stuck in one problem. I am calculating the phonon calculation of 2d material after relaxation the structure. I got the negative frequencies. How to resolve this type of errors?

I am stuck in one problem. I am calculating the phonon calculation of 2d material after relaxation the structure. I got the negative frequencies. How to resolve this type of errors?

### Re: Need a help regarding EPW calculation!!

Hello Sir,

Also, is there is any constraint on the forces that is should be very low otherwise frequencies always negative.

If yes what is the minimum of that because I got around 0.005 or less?

Also, is there is any constraint on the forces that is should be very low otherwise frequencies always negative.

If yes what is the minimum of that because I got around 0.005 or less?

### Re: Need a help regarding EPW calculation!!

Hi Sahil Dani,

For 2D systems, please check the page suggested by H. Lee at

viewtopic.php?f=3&t=1311

Regarding your phonon question, nobody knows except you without input/output information. Try to provide some details on this, if you want. Also, I recommend you to follow qe-forum, see if anyone already has the solution, if not you can also post your question there.

Best,

Hari

For 2D systems, please check the page suggested by H. Lee at

viewtopic.php?f=3&t=1311

Regarding your phonon question, nobody knows except you without input/output information. Try to provide some details on this, if you want. Also, I recommend you to follow qe-forum, see if anyone already has the solution, if not you can also post your question there.

Best,

Hari

Last edited by hpaudya1 on Tue May 11, 2021 7:30 pm, edited 1 time in total.

### Re: Need a help regarding EPW calculation!!

Dear Sir,

There is one problem regarding plot of resistivity plot for "Pb"

I am using the resistivity.py script that Ponce sir given in our tutorial, By using this I am calculate the resistivity graph but does not able to produce the end result because may be error in the python script.

Could you please help me regarding this.

There is one problem regarding plot of resistivity plot for "Pb"

I am using the resistivity.py script that Ponce sir given in our tutorial, By using this I am calculate the resistivity graph but does not able to produce the end result because may be error in the python script.

Could you please help me regarding this.