[Pw_forum] Defining an antiferromagnetic graphene nanoribbon

[Roberto G. A. Veiga]

Hi, Stefano:

as far as I understand, if I use a cutoff for a system made of carbons and I find it is appropriate, I should use the same cutoff for another system also made of carbons. I mean, if I use 20 Ry for carbon nanotubes and the results are fine, I could use 20 Ry for diamond, or graphene. Is it wrong my assumption?

[]s,

Roberto

Stefano Baroni <baroni at sissa.it> wrote: The kinetic-energy cutoff is a property of the atomic core, NOT of the specific system (to a large extent).SB

On May 10, 2008, at 6:11 PM, Roberto G. A. Veiga wrote:

Dear Stefano:

I'm using Ultrasoft PPs. My question was because this cutoff (20 Ry) seemed to be appropriate for other carbonic systems.

[]s,

Roberto

Stefano Baroni <baroni at sissa.it> wrote: 
On May 9, 2008, at 10:42 PM, Roberto G. A. Veiga wrote:

Hi, Konstantin:

thank you very much. Such a large cutoff (80 Ry) is necessary for convergence? Or maybe I'm using one quite small (20 Ry)...

it depends on the PP you are using, I guess, and certainly NOT on the actual structure you are studying. 80 Ry seems like an appropriate cutoff for moderately hard norm-conserving PP's, whereas 20 Ry sounds like appriate for many US PP's. In either case, you better check the aprporiateness by yourself, through thorough convergence tests.


Stefano





[]s,

Roberto

Konstantin Kudin <konstantin_kudin at yahoo.com> wrote:  Hi Roberto,

 Here is a ribbon input that works for sure:
https://kiev.princeton.edu/misc/rg_07.scf.in
 (get PPs from the PWSCF website)

 Good luck!
 Kostya
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Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center - Trieste
[+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)


La morale est une logique de l'action comme la logique est une morale de la pensée - Jean Piaget



Please, if possible, don't  send me MS Word or PowerPoint attachments
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