Hi, everyone. I am trying to perform the band structure calculations for the organic crystals using quantum espresso.
The first step (SCF job) is resulted with normal termination. But, there is error in "nscf" and "bands" calculation. The error is...
" Message from routine efermit:
Internal error, cannot bracket Ef
Error in routine twights (1):
bad fermi energy"
I searched for this error, and found some suggestion for increasing "nbnd" and number of K-points. I did the same for my case, but again the same error came. I tried many times with different possibility, but each time the same error displayed.
Kindly please suggest me.
Thanking You
Did you choose optimized structure coordinates for SCF and nscf calculation? If you choose optimized structure coordinates you may not get this error probably.
Next speaking about your nscf calculation, you should use higher nbnd value. For example, if you have 320 electrons in your system, then you should choose at least 400 bands in order to perform nscf calculation and K-points should be higher enough (i.e. 10*10*1 or 15*15*1).
Thanks Sai.
I have the organic crystal structure file (.cif). I think the crystal structure is itself an optimized one. So is it necessary to optimize ? But, I am not clear about this, so plz suggest.
And, I have to optimize the structure using QE ?
Next, I will try with higher nbnd and K-points value.
Again, Thanks for your suggestion.
It is better to optimize your structure first using QE. Then take the coordinates of optimized structure for SCF, nscf and further bands structure calculations. In nscf choose higher nbnd value and higher K-points mesh.
Sai Phani Kumar Vangala How do I choose nbnd for my system which has 657 electrons and 395 Kohn-Sham states as specified by pwscf?
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