[Pw_forum] not converge after 100 itration

[Bertrand SITAMTZE]

Dear Ehsan,

I think there is no need for you to increase the maximum number of iterations for self consistency. You have bad input data. The periodic replica of atoms overlap with the others!!!

Graphene is a relatively small system. I will suggest that you modify your input file to describe the system within the hexagonal symmetry (ibrav=4) and only two atoms in the unit cell and a substantial vaccum in the z-direction. This is the normal representation of graphene.

HTH,

Bertrand


 
***********************************
Bertrand SITAMTZE YOUMBI
PhD Materials Sciences

******CURRENT ADDRESS
IMMM, UMR CNRS 6283
 Université du Maine
Le Mans, France
Tél: +33 6 67 61 52 15
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Le Lundi 25 novembre 2013 10h53, Lorenzo Paulatto <lorenzo.paulatto at impmc.upmc.fr> a écrit :
 
On 11/24/2013 08:03 PM, ehsan targholi wrote:
> dear all pw users,
> my relax calculation is not converge after 100 iteration . please help me
> to find problem in input.
> my input is :

Dear Ehsan,
there is something seriously wrong with your structure: the atoms appear
to be more or less on top of each other. If I double the size of the
first two unit cell axes it looks much more reasonable. Are you sure you
did not apply the Bohr to Agstrom conversion twice?

P.S. you normally need a small smearing to converge graphene. I think
there is a discussion of this in Phys. Rev. Lett. 93, 185503 (2004)


-- 
Dr. Lorenzo Paulatto
IdR @ IMPMC -- CNRS & Université Paris 6
phone:+33 (0)1 44275 084 / skype: paulatz
www:  http://www-int.impmc.upmc.fr/~paulatto/
mail: 23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 5

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