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 -----????----- 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 _______________________________________________ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum