[Pw_forum] graphite cell optimization failed

[giuseppe.mattioli at mlib.ism.cnr.it]

Dear all
You can do better than the semiempirical "Grimme" correction. There is
a new ab initio van der Waals correlation functional implemented in QE
4.3a. Try    input_dft='vdW-DF', in the &sysytem list.
By the way, what about a (semiempirical or ab initio) vdW scheme in
cp.x? Is there any project going on?

Yours

Giuseppe

Quoting Masoud Nahali <masoudnahali at gmail.com>:

> Dear Eric
>
> Try london="true" to get improved answer; as you should know DFT is weak
> to calculate dispersion forces and by using the keyword one can include
> these forces semi-empirically. I hope it helps.
>
> Best Wishes
>
>  Masoud
> --------------
> Masoud Nahali, Sharif University of Technology
>
>
> Eric 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
> <http://www.democritos.it/mailman/listinfo/pw_forum>>
>
> College of Physical Sciences
> Graduate University of Chinese Academy of Sciences
> Yuquan Road 19A
> Beijing 100049
> China
>

Giuseppe Mattioli
ISM-CNR
Italy