[Pw_forum] graphite cell optimization failed

[Gabriele Sclauzero]

Dear Giuseppe,

   is there any concrete evidence that "ab initio" van der Waals vdW-DF is systematically better than Grimme's vdW?
Are you aware of any paper comparing the latest version of the two methodologies (or "phisolophies", if you want), i.e. vdW-DF2 vs DFT-D3?

Cheers,

GS


Il giorno 23/mar/2011, alle ore 10.12, giuseppe.mattioli at mlib.ism.cnr.it ha scritto:

> 
> 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
> 
> 
> 
> 
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§ Gabriele Sclauzero, EPFL SB ITP CSEA
   PH H2 462, Station 3, CH-1015 Lausanne

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