[Pw_forum] query on fermi energy

[Peter Wang]

for the first question, there is no absolute Fermi energy. The only absolute 
energy is that substracting vacuum energy level from it.

best
Yun-Peng

-----原始邮件----- 
From: Ajit Vallabhaneni
Sent: Saturday, January 14, 2012 3:32 PM
To: PWSCF Forum
Subject: [Pw_forum] query on fermi energy

Dear users,

          1.  I was wondering how to calculate the absolute value of fermi 
energy for graphene single layer. By varying the size of the super cell in 
the out of plane direction, i observed that the total energy is constant 
indicating no  interactions in the out of plane direction, but the fermi 
energy is varying with increasing distance. I think it is the relative fermi 
energy which is output after the scf calculation. I want to know the 
absolute value.


           2.  Another question i have is regarding the e-ph calculation. 
For a give set of q and k points, what is the best way to ensure that all 
k+q points are available to avoid the message " q is not a vector in the 
dense grid" in the calculations"? I observed that using a dense grid is not 
enough sometimes. Do we have to check it outside of the quantum espresso 
before the calculation begins?


Thanks
Ajit
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