[Pw_forum] graphite cell optimization failed

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

Dear Gabriele

>    is there any concrete evidence that "ab initio" van der Waals   
> vdW-DF is systematically better than Grimme's vdW?

Yes, at least in the case of molecule-surface interactions. There is a  
recent (2010) Grimme paper (I'm sorry, I cannot be more accurate  
today...) that reports an overestimate of the above interactions when  
using DFT-D2, currently implemented in QE. I've performed comparative  
tests (classical MM, DFT-D2, vdW-DF) on several molecules interacting  
with the non-polar 10-10 ZnO surface and I've obtained the best  
results (some of them comparable with experimental data, i.e., the  
thiophene ring) by using the vdW-DF approach. The DFT-D2 setup,  
however, is quite good for molecules in my experience, and can be  
tuned by changing the C6 coefficients by hand  
(QE/Modules/mm_dispersion.f90), following one of the available force  
fields (AMBER, CHARMM, ...). Maybe DFT-D3 and vdW-DF would converge to  
similar results...
What about cp?

Yours

G.

Quoting Gabriele Sclauzero <sclauzer at sissa.it>:

> 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
>>
>>
>>
>>
>> _______________________________________________
>> Pw_forum mailing list
>> Pw_forum at pwscf.org
>> http://www.democritos.it/mailman/listinfo/pw_forum
>
>
> § Gabriele Sclauzero, EPFL SB ITP CSEA
>    PH H2 462, Station 3, CH-1015 Lausanne
>
>