[QE-users] dielectric constant calculation

[Christoph Wolf]

Dear Jay,

for graphene you will need a much finer k-grid, for phonons people often
use 72x72 or 96x96 grids to get close to the Dirac point.

DFPT on graphene is also a bit tricky due to its semi-metallic character;
try with smearing instead of treating it as an insulator, of course metals
have infinite dielectric constants as they screen everything instantly but
as I do not know what you are trying to achieve exactly this is the first
thing that comes to mind.

I also recommend to use an ibrav other than 0 so that QE does not have a
hard time recognizing the symmetries, I have encountered some situations
where this helped a lot.

HTH!
Chris

-- 
Postdoctoral Researcher
Center for Quantum Nanoscience, Institute for Basic Science
Ewha Womans University, Seoul, South Korea
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