The ABINIT Users Mailing List ( CLOSED )

[matthieu verstraete <matthieu.jean.verstraete@gmail.com>]

>>>
>>> 1) is your system metallic? And do you have enough unoccupied bands.
>>> It sounds like the rest of your things are well converged, so I'll
>>> presume so.
>>>
>> The system is metallic. Single band system at Fermi level. I had about 8
>> bands above the Fermi level in the initial ground state SCF calculation.
a few more might be needed - still we need to see the occupations and
the convergence of the ETOT for the phonon runs...


>>>
>> I am trying to address this in my new calculation by using a 16x16x16 grid
>> with shiftk 0.0 0.0 0.5 (since the unit cell is hexagonal) for both the
>> ground state and rf calc.
>> One question I have is: If my q-vector for the rf calc of the density
>> matrix is Gamma then should the Gamma pt. (0.0 0.0 0.0) be a part of the
>> k-pt grid? I have not been able to figure this out from the tutorials.
no -it only has to be a difference of k-points in the grid. For el-ph
calculations, however, you _do_ have to use a zone centered grid (for
the moment at least - I am trying to see if things work otherwise).
Have you tried the phonons with 8x8x8+4shift k-points?

>>
>> A further question is on tractability. Ultimately one of my goals is to
>> calculate the electron-phonon coupling of the material. With 13 atoms in 
>> the
>> unit cell there are many displacements. ABINIT does not have ultrasoft
>> pseudopotentials and so calculations can be long. I have access to a 
>> cluster
>> where I may use up to 64 cores for a max of 12 hours. Should this sort of
>> problem be tractable in ABINIT?
probably, though it's hard to say. How long does your ground state
take? For el-ph the k-point convergence can be a real pain (read as
"need much more than 16^3").


Cheers

Matthieu

PS: PAW phonons are coming soon.