[Pw_forum] Relaxation of low symmetry lattices

[Lorenzo Paulatto]

On Fri, October 9, 2009 09:26, Manoj Srivastava wrote:
>  which is one order of magnitude smaller than before :) but the KE cutoff
>  is ridiculously high! I also increase k points with keeping KE cutoff 50
>  Ry, and that gave me -

Your initial choice of k-point grid is not very wise: as you cell is much
longer in the x and y direction than in the z direction you will need more
points in z than in x and y. I would say about 2 - 3 times as many. e.g.
you could choose:
 K_POINTS automatic
   6 6 14  0 0 0

>  Gabriele: Would you mind to tell me how can i get rid of FFT
>  incompatibility issue?

I just told you, in my previous email. Yet I don't think it's a good idea,
and the forces won't be zero anyway. Your lattice have lower symmetry than
the FCC lattice (it is actually a supercell), hence you can only have zero
forces up to the numerical accuracy.

best regards


-- 
Lorenzo Paulatto
SISSA  &  DEMOCRITOS (Trieste)
phone: +39 040 3787 511
skype: paulatz
www:   http://people.sissa.it/~paulatto/



----------------------------------------------------------------
  SISSA Webmail https://webmail.sissa.it/
  Powered by SquirrelMail http://www.squirrelmail.org/