Can the "nscf" and "bands" result in different OAS?

[sdwang]

Dear developers:
I use pwscf interface to link to yambo.When I select "scf" and "nscf" procedures, its result of OAS without local fields effects is different the "scf", "bands" one, is anybody encounter this situation?
Another question:for k-points in input file
K_POINTS (automatic)
6 6 1 0 0 0
when the flag shiftk is "0 0 0 ", its result of OAS is different "1 1 0", which one is more believable?

Thanks!

[Daniele Varsano]

Dear Shudong,

Another question:for k-points in input file
K_POINTS (automatic)
6 6 1 0 0 0
when the flag shiftk is "0 0 0 ", its result of OAS is different "1 1 0", which one is more believable?

In this way you are sampling different k-points in the Bzone. When you are at convergence with the number of
k-point they will give the same result. The same is true when doing a "band" or "nscf" calculations, if they are
calculated with the same accuracy, and the same k-point sampling they have to give the same result.

Best,

Daniele

[sdwang]

"In this way you are sampling different k-points in the Bzone."
What does this mean? I am sorry I can not understand it.My unit is 2D with a vaccum slab, so I chose 6 6 1 k-ponit.
Do you mean my k-point is not at convergence levell?
Thanks!

[Daniele Varsano]

Do you mean my k-point is not at convergence levell?

I can't know it! You should check it!! Anyway if you have a look at your pwscf ouput of
to the Yambo report, you can see that the K-point is different, when you use a shifted or
not shifted grid. Consequently in your spectrum, even the non interacting one (Fermi Golden Rule)
contains different transitions (and may be you should be able to recognize them!).
When at convergence the differences should vanish.

Best,

Daniele

[andrea marini]

"In this way you are sampling different k-points in the Bzone."
What does this mean? I am sorry I can not understand it.My unit is 2D with a vaccum slab, so I chose 6 6 1 k-ponit.
Do you mean my k-point is not at convergence levell?
Thanks!

Dear Shudong,

to run Yambo you need, at least, some basic concepts about solid state physics. Please spend some time reading any textbook about the subject you can find in your local librabry. You should concentrate on the concept of Brillouin Zone sampling.
Moreover did you check on the PW documentation/forum the difference between using "shifted" or "unshifted" grids before using them ?