[Pw_forum] graphite cell optimization failed

[Eric Germaneau]

Dear QE users,

First of all I thank you all so much for your very useful replies and 
advices.
I did again the calculation this time using 16x16x8 k-points with cold 
smearing  as suggested in PRB 71, 205214 (2005).
I've also increased the precision of the atomic coordinates.
Finally, I preformed the calculation using GGA only, GGA+london, and LDA.
I got the following results:

GGA                             GGA - 
london                                
LDA                                                             EXP

a = 2.46854 angs       a =  2.46283 angs                          a = 
2.44424                                         a = 2.46067
c = 8.02141 angs       c =  6.39949 angs                          c = 
6.49579                                         c = 6.705 (6.67 at 0K)
energy = -155.032      energy =  -155.146 ev/atom           energy = 
-155.481 ev/atom

The DFT-D approach improve significatively the length of the c axis.
I'm currently trying to do the same thing with the vdW-DF method 
implemented in QE 4.3a but the program crash with the error:

/     from ggen : error #     45126
      too many g-vectors/

Best,

              Eric.

On 03/23/2011 12:33 PM, Eric Germaneau wrote:
> Dear all,
>
> I'm trying to optimize unit cell parameter of graphite.
> The problem is the c axis gets too long.
> Starting from published data my initial parameters are a=4.59203 Bohr 
> and c=12.513 Bohr.
> The final values are 4.664 and 15.829 respectively.
> I need someone to explain to me what I did wrong, I've attached my 
> input file.
> That's a basic calculation so it's very frustrating to not make it done.
> I thank you in advance,
>
>                                     Eric.
>
> -- 
> /Be the change you wish to see in the world
> / --- Mahatma Gandhi ---
>
> Dr. Éric Germaneau <mailto:germaneau at gucas.ac.cn>
>
> College of Physical Sciences
> Graduate University of Chinese Academy of Sciences
> Yuquan Road 19A
> Beijing 100049
> China
>
> /Please consider the environment before printing this email.
> Considérez svp l'environnement avant d'imprimer cet email. /
>
>
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-- 
/Be the change you wish to see in the world
/ --- Mahatma Gandhi ---

Dr. Éric Germaneau <mailto:germaneau at gucas.ac.cn>

College of Physical Sciences
Graduate University of Chinese Academy of Sciences
Yuquan Road 19A
Beijing 100049
China

/Please consider the environment before printing this email.
Considérez svp l'environnement avant d'imprimer cet email. /

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