[Pw_forum] Cu US PP with PBE exchange

[Eyvaz Isaev]

Hi, 

20 Ry, definitely, is not enough. It should be,
perhaps, about 30-35Ry. You can try to do some tests
for total energy calculations, say, for experimental
lattice parameter with increasing Encut. When you have
converged with this you can recalculate lattice
parameter using converged Encut.

K-sampling should be enough, but again, you can try
more fine k-mesh.

Bests,
Eyvaz.
  
--- "Hong, SamPyo" <likedew at phys.ksu.edu> wrote:

> Hello,
> Just for a test purpose, I picked up the
> pseudopotential
> 'Cu.pbe-d-rrkjus.UPF' for Cu bulk, which I
> downloaded from web.
> The known experimental a0 is 3.61 Angstrom but I
> could get at best 3.80
> angstrom, which is huge off from the value.
> I wonder why this PP performs that poorly.....I
> think ecut of 20 ryd and
> k-sampling of 15x15x15 should be enough for test.
> Does anybody have an idea?
> 
> Best regards,
> 
> Sampyo
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